is because about 6 months ago Ytube updated their app and the old apps no longer work that well, unless you continually do that 'clear cache' thing (which you can't do on them Mag models)
The proper fix is to update the Ytube app thru Google Playstore, but again unfortunately you can not access Google Playstore thru them Mag models, nor can you side load the apk version on them Mag models.
You can easily find the current apk/app version thru an online search