Adding SPLINE to DXF makes the file corrupt (content not shown)

I am working on my own DXF writer because I only need certain elements (such as LINE, POLYLINE, POINT an SPLINE).

I started with tfpdxfbridge and the idea was to include SPLINE support too. When I tried to manually add SPLINE to ENTITIES in the *.dxf file, the file is not opened anymore. Example of SPLINE:

    SPLINE
  5
274
330
1F
100
AcDbEntity
  8
0
100
AcDbSpline
210
0.0
220
0.0
230
1.0
 70
     8
 71
     3
 72
     9
 73
     5
 74
     0
 42
0.0000000001
 43
0.0000000001
 40
0.0
 40
0.0
 40
0.0
 40
0.0
 40
1.0
 40
2.0
 40
2.0
 40
2.0
 40
2.0
 10
747.2822841342859
 20
1453.676625339077
 30
0.0
 10
1364.898523055965
 20
2324.178049512178
 30
0.0
 10
2830.924436828291
 20
1999.364085075557
 30
0.0
 10
1130.854480067877
 20
862.5152127789023
 30
0.0
 10
2837.42565094653
 20
791.0561394394999
 30
0.0
  0

Does anybody know what the problem might be or how to make the file work again?

Here is the full file generated with tfpdxfbridge (except the SPLINE part, obviously).

0
SECTION
2
HEADER
999
Generator: TFPDxfWriteBridge
999
By jmpessoa@hotmail.com
9
$DIMASZ
40
0.1800
9
$DIMTSZ
40
0
9
$DIMGAP
40
0.0900
9
$DIMEXO
40
0.0625
9
$DIMDLI
40
0.38
9
$DIMDLE
40
0.0
9
$DIMEXE
40
0.1800
9
$DIMTXT
40
0.1800
9
$DIMTXTDIRECTION
70
0
9
$DIMTIH
70
1
9
$DIMTAD
70
0
9
$DIMCLRD
70
256
9
$DIMCLRE
70
256
9
$DIMCLRT
70
256
9
$DIMASO
70
1
9
$DIMASSOC
280
2
9
$DIMSHO
70
0
9
$DIMLUNIT
70
2
9
$DIMDEC
70
4
9
$DIMADEC
70
2
9
$INSBASE
10
0.0
20
0.0
30
0.0
9
$EXTMIN
10
0.0
20
0.0
9
$EXTMAX
10
3200.0
20
3200.0
9
$LINMIN
10
0.0
20
0.0
9
$LINMAX
10
3200.0
20
3200.0
0
ENDSEC
0
SECTION
2
TABLES
0
TABLE
2
LTYPE
70
8
100
AcDbSymbolTable
100
AcDbLTypeTable
0
LTYPE
2
CONTINUOUS
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
____________
72
65
73
0
40
0.000
70
0
0
LTYPE
2
HIDDEN
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
__ __ __ 
72
65
73
2
40
0.375
49
0.250
49
-0.125
70
0
0
LTYPE
2
CENTER
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
____ _ ____ _ 
72
65
73
4
40
2.000
49
1.250
49
-0.250
49
0.250
49
-0.250
70
0
0
LTYPE
2
DOT
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
. . . . . 
72
65
73
2
40
0.250
49
0.000
49
-0.250
70
0
0
LTYPE
2
DASHDOT
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
__ . __ . 
72
65
73
4
40
1.000
49
0.500
49
-0.250
49
0.000
49
-0.250
70
0
0
LTYPE
2
DIVIDE
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
____ . . ____ . . 
72
65
73
6
40
1.250
49
0.500
49
-0.250
49
0.000
49
-0.250
49
0.000
49
-0.250
70
0
0
LTYPE
2
BORDER
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
__ __ . __ __ . 
72
65
73
6
40
1.750
49
0.500
49
-0.250
49
0.500
49
-0.250
49
0.000
49
-0.250
70
0
0
LTYPE
2
MJLINE
100
AcDbSymbolTableRecord
100
AcDbLinetypeTableRecord
3
__ __ __ 
72
65
73
2
40
0.375
49
0.250
49
-0.125
70
0
0
ENDTAB
0
TABLE
2
STYLE
70
2
100
AcDbSymbolTable
100
AcDbStyleTable
0
STYLE
2
DEFAULT
71
0
40
0.00
42
1.00
50
0.00
41
1.00
3
ARIAL.TTF
100
AcDbSymbolTableRecord
100
AcDbTextStyleTableRecord
70
0
0
STYLE
2
ISOCPEUR
71
0
40
0.00
42
1.00
50
0.00
41
1.00
3
isocpeur.ttf
100
AcDbSymbolTableRecord
100
AcDbTextStyleTableRecord
70
0
0
ENDTAB
0
TABLE
2
LAYER
70
9
100
AcDbSymbolTable
100
AcDbLayerTable
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
0
70
0
62
7
6
CONTINUOUS
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
HIDDEN_YELLOW
70
0
62
2
6
HIDDEN
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
CENTER_RED
70
0
62
1
6
CENTER
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
DOT_GREEN
70
0
62
3
6
DOT
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
DASHDOT_CYAN
70
0
62
4
6
DASHDOT
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
DIVIDE_BLUE
70
0
62
5
6
DIVIDE
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
BORDER_MAGENTA
70
0
62
6
6
BORDER
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
CONTINUOUS_GRAY
70
0
62
8
6
CONTINUOUS
0
LAYER
100
AcDbSymbolTableRecord
100
AcDbLayerTableRecord
2
MYLAYER
70
0
62
5
6
MJLINE
0
ENDTAB
0
TABLE
2
DIMSTYLE
70
2
100
AcDbSymbolTable
100
AcDbDimStyleTable
0
DIMSTYLE
100
AcDbSymbolTableRecord
100
AcDbDimStyleTableRecord
2
GENERIC
70
0
77
0
176
256
177
256
178
256
41
0.18
46
0.00
44
0.18
42
0.06
147
0.09
140
0.18
3

4

5

6

7

40
1.0
43
0.38
45
0.0
47
0.0
48
0.0
141
0.09
142
0.0
143
25.39999
144
1.0
145
0.0
146
1.0
71
0
72
0
73
1
74
1
75
0
76
0
78
0
170
0
171
2
172
0
173
0
174
0
175
0
0
DIMSTYLE
100
AcDbSymbolTableRecord
100
AcDbDimStyleTableRecord
2
CUSTOM
70
0
77
0
176
3
177
3
178
3
41
0.18
46
0.00
44
0.18
42
0.06
147
0.09
140
0.18
3

4

5

6

7

40
1.0
43
0.38
45
0.0
47
0.0
48
0.0
141
0.09
142
0.0
143
25.39999
144
1.0
145
0.0
146
1.0
71
0
72
0
73
1
74
1
75
0
76
0
78
0
170
0
171
2
172
0
173
0
174
0
175
0
0
ENDTAB
0
ENDSEC
0
SECTION
2
BLOCKS
0
ENDSEC
0
SECTION
2
ENTITIES
0
CIRCLE
100
AcDbEntity
8
BORDER_MAGENTA
62
256
6
BYLAYER
39
0.00
100
AcDbCircle
10
6.00
20
4.00
30
0.00
40
1.20
0
ARC
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbCircle
10
10.00
20
6.00
30
0.00
40
1.20
100
AcDbArc
50
10.00
51
80.00
0
POLYLINE
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
100
AcDb2dPolyline
70
0
66
1
0
VERTEX
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
0.00
20
0.00
30
0.0
0
VERTEX
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
0.00
20
3.00
30
0.0
0
VERTEX
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
1.50
20
1.50
30
0.0
0
VERTEX
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
3.00
20
3.00
30
0.0
0
VERTEX
100
AcDbEntity
8
MYLAYER
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
3.00
20
0.00
30
0.0
0
SEQEND
0
POLYLINE
100
AcDbEntity
8
DOT_GREEN
62
256
6
BYLAYER
100
AcDb2dPolyline
70
1
66
1
0
VERTEX
100
AcDbEntity
8
DOT_GREEN
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
-1.00
20
-1.00
30
0.0
0
VERTEX
100
AcDbEntity
8
DOT_GREEN
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
-1.00
20
4.00
30
0.0
0
VERTEX
100
AcDbEntity
8
DOT_GREEN
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
4.00
20
4.00
30
0.0
0
VERTEX
100
AcDbEntity
8
DOT_GREEN
62
256
6
BYLAYER
39
0.00
100
AcDbVertex
100
AcDb2dVertex
10
5.00
20
-3.00
30
0.0
0
SEQEND
0
ENDSEC
0
EOF

Solution

When I try to recover your DXF file I get the following:

Unknown header variable $LINMAX ignored on line 116.

Undefined group code 330 for object on line 1018.

Invalid or incomplete DXF input -- drawing discarded.

In your DXF you have:

330
1F

I see that 330 is included when I do my own spline and save as DXF. But, 330 is according to the documents:

Soft-pointer ID/handle to owner dictionary (optional)

This DXF will recover without any errors:

https://pastebin.com/KRpzCd4M

Perhaps you can do a comparison.