https://a.co/d/94hdkPH
Was replacement block a new one? There is a o- ring
and flat white washer in the block, they should be replaced, also is worth checking the spring, and ball in the tube. Make sure there is a tight connection, do not oversight. These hydro-force sprayers can behave weirdly at times. I have 4 of them, only two are working as of now. When you said that the filter is clean, what do you mean? You should have three filters, one before the block ( in QD), one after the block where the hose meets the handle, and one before T-jet at the end of spraying wand. You can submerge the block in the descaler, or the vinegar( take out the o-ring and plastic washer) and following day blow the gunk out of it. Sometimes Teflon gets in the system and causes the problem, cracked delivery tube has to be cut and shortened if possible. So when the venturi effect is disrupted you might have a problem. It's worth mentioning that at higher pressure you get more water, and less chemistry dispersed, with lower pressure is the opposite. In some cases, hot water coming through the injection sprayer eliminates mixture delivered and you're pre-spraying with hot water only. Too many variables...
I hope this helps. I have 10 blocks on hand, I've ordered another a few minutes ago, and you should too, the price is unbeatable.