Steps to reproduce
- Go to Settings > Security
- Enable 'Encrypt to verified devices only'
- Go back to a DM with one of your contact, click on his profile
- Tap on verify.
Outcome
What did you expect?
That you initiate a verification process.
What happened instead?
It's failing because the recipient won't be able to decrypt the verification request

So it's quite annoying, I enabled 'Encrypt to verified devices only' and I have unverified users in a room. So you would think that verify them will fix the issue, but you can't