Repro path:
- Create two non-flying tokens (in my case it was Kiora octopus and an embalmed Temmet
- Opponent puts a Sandwurm Convergence onto the battlefield
- Create an Aven Wind Guide that grants your initial token flying (in my case it was an embalmed one but I guess non-embalmed could react the same) → naturally all tokens are now unable to attack
- Replace the Aven Wind Guide with another creature (in my case it was a non-token Temmet)
- My token creatures lose flying
Expected: My token creatures are able to attack since they are no longer fliers
Actual: My token creatures are still unable to attack due to Sandwurm Convergence’s continuous effect.
Once I removed Convergence from the board, they returned back to normal of course.
Edit: Whoopsie, it seems I posted it in the wrong section. Sorry about that 
//Edited Title -Brigby