I haven't heard much about Dissolve (https://dissolve.com/). Does anybody submit videos there? How are earnings relative to other sites? Any reasons to avoid them or bad experiences?

Submit enough materials it'll make money for you. YOu must have the stamina to last the distance.

They also require you to sign a contract for a number of years, so you can't just go and leave if you want. At least that was the case when I signed up with them in 2014, I don't know whether that's still the case now.
The bad thing about that is the fact that you don't have control over your footage on the platform, so you can't edit or delete anything, every change has to go through their support. As long as you don't plan on going exclusive somewhere else, I guess it's not much of a problem, but for me it was when I wanted to go exclusive on Pond5 last year. They even went beyond the date the contract expired, even though I had sent my notice of termination months in advance, because they told me that some of my assets were still in someone's cart and that the customer would need to be notified (and given like a 2 or 3 week grace period afterwards). They couldn't have done that 2 or 3 weeks in advance of the termination date? No, of course not...

My advice: avoid.

My videos on this stock are selling very poorly. Is anyone happy with the sales?

Not a single sale in one year. I don't think they are even functioning

I want to delete my account there but they are just not answering my e-mails and I can't do it alone. They keeps your files forever? I don't like that

I don't upload to dissolve, it doesn't sell well.