Trouble with AE CS4

My old program is acting up.  I'm using CS4 with Sierra 10.12.6 on a Mac Mini 2014.

I also use it on a Mac Pro with Snow Leopard 10.6.8 and it works fine.

I prefer using the Mini because of its speed and Apple keyboard.

The problem occurs spontaniously.  It jumps in magnification while working on projects and sometimes gets locked up when trying to quit.  I am forced to force quit at those times.

I'm retired and enjoy using CS4 for family related projects and do not need the additional effects and/or speed offered with updates.  I'm also on fixed income and the added expense is not within my budget.

Today, I uninstalled and reinstalled the program hoping it would solve the problem.  It didn't.

I hope someone out here can offer suggestions on whether or not this can be corrected.

Thank you.