Author Cannot properly edit/add/remove tags or genres in Firefox. Fixed
1. As the title says, I cannot properly edit/add/remove tags, genres in Firefox (62.0.3). This hasn't happened before when using this browser, and I've not installed any new addons that may interfere.

At the moment, when I click "Edit" on a page, ALL tags don't show up. It only allows me to add 1 tag if I try to re-add it, but when I click the dropdown menu again to add another, it only switches to that other tag instead of adding a new in the end I can only have 1 tag before saving. Of course, when I noticed this, I tried this on other browser to try and fix it: Opera and Chrome still work as normal.

2. Since I'm here, I may as well report that I cannot Unfollow a series on Firefox, but all the other buttons still work under the Follow dropdown menu. Same situation: other browsers work as normal (which is how I've been unfollowing a series) at th it's not totally a big deal, but slight inconvenience nonetheless.
Try clearing cache.
If that doesn't work, try clearing cookies too.
I have the same problem, don't know if it's related to my browser. I do use Firefox though.

I can't edit series like Futanari no Elf and Sakura-chan to Amane-kun. The edit button is greyed out. Is this a user level issue? I just want to add webcomic tag to those two.
@Arashiyama The edit button is locked, so only mods can edit. You can use the report button to ask for changes, they usually change it quite fast
Tried that. Still nothing. Even tried updating my browser to latest, and trying with all add-ons turned off. Still the same situation.

Not an issue of locked pages. This is for every page.
Screw it. I did a clean uninstall/reinstall (losing all my preferences in the process) but it all works again. I think an old Firefox setting may have been still lingering around even after updating, but at any rate, it's back to normal.

Of course, I didn't forget to back up my bookmarks, since that's the only thing that really matters here.

This thread can be locked/marked as solved now.