Extremely slow loading of a page on a new tab (30s-2m) after some time of running MAC

[itisafrickinhighlander]

• Multi-Account Containers Version: 8.0.1(issue present for more than month)
• Operating System + Version: Windows 10 21H1
• Firefox Version: 94.0.1 (applicable since 93.0, which was about the version I was running at that time)
• Other installed Add-ons + Version + Enabled/Disabled-Status:

Auto Tab Discard | 0.4.7 | true
Automatic Spell Checking Language Selection | 1.0 | true
Bing | 1.3 | true
Bitwarden - Free Password Manager | 1.54.0 | true
CanvasBlocker | 01.06.2001 | true
ClearURLs | 1.21.0 | true
Cookie AutoDelete | 03.06.2000 | true
Facebook Container | 02.03.2001 | true
Firefox Color | 02.01.2007 | true
Firefox Multi-Account Containers | 8.0.1 | true
HTTPZ | 0.12.0 | true
Privacy-Oriented Origin Policy | 01.04.2002 | true
Skip Redirect | 02.03.2005 | true
Stylus | 01.05.2021 | true
Tab Session Manager | 06.11.2001 | true
uBlock Origin | 1.38.6 | true
uMatrix | 01.04.2004 | true
Web Archives | 02.01.2000 | true
Wikipedia (en) | 1.1 | true

Actual behavior

Sync feature is on. I use two PCs, each is running FF with my actual FF account:

First PC, my Windows VM (less powerful, 4 CPU threads, 6GB of RAM) in the work - after some time it starts taking 30 seconds to 2 minutes to load a web page on a new tab; when I disable MAC, it always immediately loads anything which would be taking time to load, many time re-enable will not immediately cause websites to again take so long to load, but after 10 minutes to 2 hours this would start happening again.
Restarting FF helps, but again, with varying success, sometimes it is fine even until next day (FF is on all the time), sometimes even after a couple of minutes issue manifests again.

My other PC, (powerful) desktop at home shows this in much much lesser extent, sometimes this happens only once in a couple of days (PC is also almost always on), but if it happens, disabling MAC fixes the issue, re-enabling breaks it and restart of FF is required.

Expected behavior

Websites load normally and fast as they should.

Steps to reproduce

1. run FF
2. wait
3. when pages on new tabs load extremely slow, disable MAC, it fixes it, re-enable it and it might immediately start loading them extremely slow
4. reboot FF and it will work for a while just fine

Notes

Issue started showing up first on that first PC a couple of weeks after I set up FF there (that VM is active for almost 4 months), before that this wasn't happening at all.

Suggested fixes like this one here
stoically/temporary-containers#371 (comment)
doesn't work, it returns error, that "tmp is not defined".

Also, this
#1675 (comment)
is not my case, I checked containers.json and there are only my custom ones.

Last one, I use MAC for more than a year I think and I never had any issue with it until I started using that second PC and now it seems to affect all instances, but in a varying degree.

If anyone thinks it could help I would have no problems resetting the whole MAC. I use about 7 containers (I kept only one of default ones), it wouldn't be that much work to set them up again, but I don't know how to do so.

[StegaNetworks]

Experiencing the same thing on Mac. Upwards of 2 minutes to load new tabs, or refresh existing ones even.

Disabling the plugin makes the tab load instantly. I have been disabling / enabling it every half-hour or so as things get unusable, to try to keep it running.

Mac OS 12.0.1
Sticky Window Containers 1.0.4
Multi-account containers Version 8.0.1
FF 94.0.1

[StegaNetworks]

Should also stipulate that the MAC toolbar won't open anymore either. I can however still see the list from the new tab + icon.

[swentel]

I've been experiencing delays too on FF and linux, with the 8.0.2 release.
Not sure from which version I came originally (I don't update automatically) - will try and revert to an earlier version to see if that helps.

edit : reverted to 8.0.1 and that was better, going back to 7.4.0 was even better in terms of speed.

[ybrhue]

I have the same issue on manjaro linux, running kernel 6.1 and plasma.

I also use profile-sync-daemon to run FF in memory (I have over 40GB Ram).

Just unbelievable how slow container tabs are.