iOS UI testing issues with multiple destination

I’m trying to run my UI tests on a set of destinations. And my builds usually failing because Travis can’t start or connect to simulator. I would like to run tests for 8-10 destinations (in parallel ideally). But for now it can only handle 3-4 destinations with disabled concurrent testing.

Also some time tests failing by timeout (waiting for UI element to exist more that 5 secs) which means they are running very slow.
Are there any performance limitations which i exceeded ?

Also i don’t like to use jobs matrix because i want to deploy after all tests succeeded.

Failed build example:

Many thanks for any advice.