I just set up a local instance of Invidious. I created an account, exported my YouTube subscriptions, and imported them into Invidious. The first time I tried, it imported 5 subscriptions out of 50 or so. The second time I tried, it imported 9.
Thinking there might be a problem with the import function, I decided to manually add each subscription. Every time I click "Subscribe," the button will switch to "Unsubscribe," then immediately switch back to "Subscribe." If I look at my subscriptions, it was never added.
My first thought was a problem with the PostgreSQL database, but that wouldn't explain why some subscriptions work when I import them.
I tried rebooting the container, and it made no difference. I'm running Invidious in a Ubuntu 22.04 LXC container in Proxmox. I installed it manually (not with Docker). It has 100GB of HDD space, 4 CPU cores, and 8GB of memory.
Had this issue on different instances. Through trial and error I discovered that if I move my mouse off the subscribe button fast enough, it won't unsubscribe. I'm thinking the event is firing multiple times with some mouse-over and not mouse-down event. Often a page reload fixes that issue for me.
I used Invidious for about a year and it was a constant string of bugs. Every release was a risk and quite often updates would get lost or the database would explode in size and consume all the drive space. Its not a project I currently use or recommend until it stabilises.
I decided to give up on it. Looking through the docs, they recommend that due to "reasons," it should be restarted at least daily, preferably hourly. I don't know if they have a memory leak or some other issue, but that was reason enough for me not to use it.
I installed TubeArchivist, and it suits my needs much better. Not only do I get an archive of my favorite channels, but when a new video is released, it gets automatically downloaded to my NAS and I can play it locally without worrying about buffering on my painfully slow internet connection.