Okay, thanks! Another thought, but do you have similar issues if you are the one hosting?
Unfortunately, if you’ve exhausted all of our connectivity solutions linked above, then I’m at a bit of a loss. There may be increased instability in general due to the mobile data connection - but it’s difficult to be certain with many factors involved.
I can understand that it’s not ideal, but in this situation I’d be happy to contact Steam and assist with a refund. Please let me know if this is something you’d wish to do.