I have same problem on iOS 12.4.7 iPad air, been on most related forums , twittwr, red dot and on one cares, had 1 sort f answer which suggested 1th ram is the problem but nothing to back that up or provide advice.
I fear you are probably wasting your time posting ANYWHERE, as no one seems to give a can anyhow.
I posted a feedback on the test flight app,not to get an email
from Jagex to say post on the the mobile testing forums here, good JOKE, no Jagex people appear to look at the forums any more as lots of cmods state when other issues come up.
Sadly unless you buy the latest PC, phone, tablet you won't be able to play
I know what I want to do, but can rarely achieve it
06-Jun-2020 10:11:49