Scriptmerger removes "version number in filenames"
Due to caching reasons a version number parameter is added to all assets (JS and CSS) by default in TYPO3. The Install Tool offers a configuration for this: [FE][versionNumberInFilename] = querystring
Included Javascript as it should be:
<script src="fileadmin/JS/my-javascript.js?1544029367" type="text/javascript"></script>
Apparently scriptmerger removes these parameters. After installing scriptmerger (DEACTIVATED for JS via typoscript - that means no merging or minifying at all) script tags look like:
<script src="fileadmin/JS/my-javascript.js" type="text/javascript"></script>
The parameter that avoids caching problems is now missing...
scriptmerger version 5.0.1 to 5.3 affected (TYPO3 7.6.32)
(In some cases uninstalling and reinstalling scriptmerger solved the problem ... at least for a while. But the issue occures again after some time.)