[Coco] ML Question: MMU Block Switching

[William Mikrut]

I do have a another ML question about memory block switching.
When processing I will have a controlling program setup at $1200

        orcc     #$50    Interrupts off
lda $ffa1     Load current page
anda   #63
pshs a           Push for later
lda #$36 Map in Hi-res Text
sta $ffa1     Tell MMU to switch page
andcc  #$ef      Interrupts on

Now I can manipulate data in $2000-$3FFF and essentially display text on
the hi-res text screen.

When I am done and ending the program I cleanup with this:
        orcc #$50
puls a
sta $ffa1
andcc  #$ef

Is there any reason that would cause a program fault while my lower memory
program is operating and the MMU is set to map in page 36 to $2000-$3FFF?

My lower memory program is no where near $2000 in ending size.