It loads the EPG without issue, it just keeps disappearing? I have tried with only 2 catagorys only and does the same thing, my Z11 pro and even my firestick with tivimate keep the epg and never have to reload them or disappear for 10 seconds etc
Youn can try different dns, but it don't always help.
Android settings, ethernet, private dns and choose quad9 9.9.9.9 or google or cloudfare and test it.
And if you have xtream codes api connection. (Url, username and password)
Go to mytvonline3, menu, Contentmanager, contentsource, choose your sub and edit it With the pencil icon.
Set epg interval to 3 hours and then on bottom click on update! (Otherwise it won't save it)