TYPO3 Core

I've created a Flexform with sections to upload a (theoreticaly) unlimited amount of images in one content element. The problem is:

if i have already uploaded 19 images, the 20th image (and all images beond 20) can only uploaded, if this element is between the first 19 elements in flexform. If these elements are at the end of the field list, no images are uploaded. the other field types are working fine, only fileupload shows this nice feature :-)

<T3DataStructure>
<meta type="array">
<langDisable>1</langDisable>
</meta>
<sheets>
<sDEF>

<ROOT type="array">
        <TCEforms>
      <sheetTitle>Partybilder</sheetTitle>
     </TCEforms>    

<type>array</type>
        <el type="array">
            <field_repeated_images type="array">
                <type>array</type>
                <el type="array">
                    <field_repeated_image type="array">
                        <type>array</type>
                        <el type="array">
                            <field_image type="array">
                                <TCEforms type="array">
                                    <label>Bild</label>
                                    <config type="array">
                                        <type>group</type>
                                        <internal_type>file</internal_type>
                                        <allowed>gif,png,jpg,jpeg</allowed>
                                        <max_size>10240000</max_size>
                                        <uploadfolder>uploads/tx_templavoila</uploadfolder>
                                        <show_thumbs>1</show_thumbs>
                                        <size>2</size>
                                        <maxitems>1</maxitems>
                                        <minitems>0</minitems>
                                    </config>
                                </TCEforms>
                            </field_image>
                            <field_alt type="array">
                                <TCEforms type="array">
                                    <label>Alt Tag</label>
                                    <config type="array">
                                        <type>input</type>
                                        <size>48</size>
                                        <eval>trim</eval>
                                    </config>
                                </TCEforms>
                            </field_alt>
                            <field_title type="array">
                                <TCEforms type="array">
                                    <label>Title Tag</label>
                                    <config type="array">
                                        <type>input</type>
                                        <size>48</size>
                                        <eval>trim</eval>
                                    </config>
                                </TCEforms>
                            </field_title>
                            <field_caption type="array">
                                <TCEforms type="array">
                                    <label>Bildbeschriftung</label>
                                    <config type="array">
                                        <type>input</type>
                                        <size>48</size>
                                        <eval>trim</eval>
                                    </config>
                                </TCEforms>
                            </field_caption>
                        </el>
                        <TCEforms type="array">
                            <label>field_repeated_image</label>
                            <config type="array">
                                <max>10</max>
                            </config>
                        </TCEforms>
                    </field_repeated_image>
                </el>
                <section>1</section>
            </field_repeated_images>
        </el>

</ROOT>
    </sDEF>
    </sheets>
</T3DataStructure>
(issue imported from #M17896)