Hi,
there are lots of misaligned / mistreated Seagulls around...
my S111-2 lens is as sharp as any other quality folder lens I have,
you can see it in the Yemen pictures, maybe the later Seagulls used chinese / japanese glass and that wasnt up the former import Carl Zeiss lens elements,
my 4B TLR with Haaiou S85 lens also is as sharp as my rolleicord...
So same guess, old chinese lenses from cold war aera good,
post 1980 ones may be misaligned (dont think that lenses are the only reason)
I am sure rangefinders or even times (gummed up?) are off...
My friend in China also has a 203 folder, its sharp as hell (watch the results)
its a very early 203 from late 1960s... (even more Zeiss parts inside)
I ve seen defective compurs caused by adjusting time after cocking...
also Copal... Never change time when a leafshutter is cocked.