My first guess is air in the system.
-Flow through the filter is the same whether moving or stalled, because pump flow is constant and it is going across the relief valve to tank while the cylinder is stalled. When you go to retract, flow is higher than pump because of the cylinder area difference. More comes out the closed side than is going in the rod side. That is maybe 25-30% more in most cylinders, usually not an issue unless the filter is way undersized.
-When you first move the lever from extend to retract there can be a big flow and pressure surge. When at 2500 psi and stalled, the oil is compressed, the hoses are ballooned up, and the circuit charges up like a big capacitor. This blips through to return when the valve is first shifted to retract. Not much flow, just in cubic inches or less, but very fast. Usually no problems, but if there is extra air it makes more flow surge and could be a problem.
-If this was a first startup I would expect air in the cylinder that got compressed like an accumulator. When you shifted the valve to retract, it sends a huge flow spike downstream. Since you had cycled a few logs that is less likely. Are the ports on the cylinder up high where the air should have been purged out by then? Or might there have been trapped air in there?
-Do you see aerated fluid in the tank? If you have a suction line leak sucking air, the aerated fluid can compress in the cylinder just like above. When you shift to retract and release the pressure it can surge the filter.
-Size of lines vs. the flow. Try a gauge on the tank line of the valve before the filter and see what the pressure restriction is.
-Direction in & out, as already noted, else the pleats blow outward and collapse and blow the can.
-Bypass valve in the head? Is it set too high? Usually not an issue as they are only designed for one or two settings of the spring. However, if the filter is installed backwards, the bypass valve won’t work, and when the pleats blow outward and plug, there is no bypass valve to function.
-If you have paper element filter, and water in the oil, the paper absorbs water (which is good to take out very small amounts of water) but it swells and closes off the pore openings. Pressure drop goes way up. Normally no worries as the filter goes into bypass, but if the filter is backwards with no bypass, it can plug/collapse outward/blow housing.
-25 micron filter GENERALLY would have less filtering and dirt holding but lower pressure drop. 10 micron is smaller openings and better filtration but maybe more pressure drop. Paper has more pressure drop, less dirt holding and less filtration than the newer glass fibers. I would use 10u. 25u is ok but crude and not desirable. And I would find a new filter supplier who doesn’t give you bs.
let us know what you find
kcj
