I myself always update the Altirra used in the gamepack for when I have a blast...
Can't say I've noticed the stagger ever but make sure the Vertical Sync option in view (edit: in Altirra) is ticked..
I've not had a single issue over the years with updating Altirra in the gamepack as the only options that get changed internally that matter to the gamepack for the updates are the command line switches that we used to make sure the games got the right settings and Phaeron has not changed those..
To be honest the only thing you can expect from using a newer Altirra with the gamepack is an improvement in gaming quality where Phaeron had updated it.
As a person who has tested the games hundreds of times in Altirra and the version that was initially used in the Gamepack I can promise there no issue with updating it in the emul\altirra\ directory to the latest one, its what's in mine and its perfectly good..
Edited by Mclaneinc, Sat Oct 27, 2018 3:47 AM.