I cannot disable the interrupts as I cannot miss a single pulse comming on them.

Then it will fail

example
U8 cnt[3]
cnt = [9,7,0] // LSB...MSB
your copy routine read cnt[0] as 9
the interrupt happens
your copy routine read cnt[1] as 8

should you attempt to display directly from the cnt[p] the effect will be the same.

The only other way you can do it will be
loop:
copy cnt[] to prnt[]
compare cnt[] to prnt[]
if different goto loop

Erik