If it's not the cylinders, it's the spool valve either not self centering (out of adjustment) or leaking past the internal spool valve seals.
Remove the linkage from the spool valve. If it still settles, linkage adjustment is good.
Spools are easily rebuild in a few hrs on the bench.
These situations, I always install valves & pressure guages on the cylinders to isolate and rule out cylinders before spending $$ on a cylinder rebuild.
If they stop creeping and pressure builds in either line at rest while running, I have a leaky spool / linkage problem.