So my question is, if there is a hotfix for this already. Maybe a mod made by a fan or another known workaround?
There was a patch last time this was an issue. No word yet on any hotfixes, but I'm also hoping for one. Unfortunately, a hotfix is very unlikely to help your current Act 1 save, since the map only loads once, apparently. As such, your map already has invisible shriekers and the hotfix is unlikely to fix it. Teleporting around them truly is your best bet for Act 1 at this point.
As for a workaround, I can only report what apparently worked last time this was an issue. From what others reported, disabling all mods before loading into a new Act for the first time will keep the issue from occurring. So, once you beat Alexandar, save the game and disable all your mods before progressing. Once you arrive in the next zone it
should be safe to re-enable your mods.