Fluid TYPO3 Flux 500 error after Image Upload from Flexform

I use TYPO3 7.6.2with Flux 7.3.0, fluidcontent 4.4.0 and vhs 2.4.0 I've made a lot of FluidTYPO3 Content Elements before. At my current project, I'll use an image / FAL upload. If I try to upload an image, I've got an Server Error 500. I cannot upload an image.

I also try it with standard code from an example like this. And here's my example, no chance to upload any image.

<flux:form id="carousel" options="{useTypoScript: 0, Fluidcontent: {sorting: 101}, group: 'FCE', icon: '{f:uri.resource(path: \'Icons/Content/Carousel.png\')}'}">

            <flux:form.sheet name="imgGallerySheetImages">
                <flux:field.inline.fal name="settings.imgGalleryFalImageItems" multiple="true"
                                       maxItems="45"
                                       collapseAll="true" />
            </flux:form.sheet>


        </flux:form>
...

I'm using this snippet at the same server, another TYPO3 (6.2) and another subdomain. It's the same server. But I've no problems in the past with it.

I also can upload 'normal' images via text&media-Content Element, but not with my flux-flexform

Solution

I found the issue to my problem at FluidTYPO3/Flux: https://github.com/FluidTYPO3/flux/issues/1013

Here's the TYPO3 Core fix: http://p.cweiske.de/270 typo3/sysext/backend/Classes/Controller/FormInlineAjaxController.php and Fluidcontnet fix: https://github.com/monosize/fluidcontent/blob/3556fe61f996fc0eec7e02e91b9c3a50071073b3/Classes/Provider/ContentProvider.php fluidcontent/Classes/Provider/ContentProvider.php

It worked fine and I hope the problem will be solved with TYPO3 7.6.3