one problem I found is that there is no form of "loop label"
which both the earlier fasm and the current fasm accept,

the earlier fasm doesnt accept "loop dword label" but
accepts eg "jmp dword label" and "call dword label",

"loop" instructions automatically decrement CX (or ECX) and terminate the
loop (don't transfer the control) when CX (or ECX) is zero. It uses CX or ECX
whether the current code setting is 16-bit or 32-bit, but it can be forced to
us CX with the "loopw" mnemonic or to use ECX with the "loopd" mnemonic.

I got around that by replacing "loop label" by

sub cx, 1
jnz dword label

(I dont use "dec" as this code isnt speed critical, I
generally avoid the unusual opcodes of 16 bit. In fact
I will probably avoid loop in future as it is too complicated
to remember: does it loop if cx goes to 0 or from 0?
yes I know the answer is to 0, but I have to look that up
which wastes time. )

loopw word label ; uses CX and IP, no prefix in 16-bit mode
loopw dword label ; uses CX and EIP, prefix 66h in 16-bit mode
loopd word label ; uses ECX and IP, prefix 67h in 16-bit mode
loopd dword label ; uses ECX and EIP, both 66h and 67h prefixes in 16-bit mode