I've now ordered several runs of PCBs from JLCPCB and they've been fine.  But on the latest batch when I use my usual RS FluxOff cleaner it's cleaning the component leads fine but is leaving residues on top of the green solder mask itself.  Tried some quite intensive washing and it's quite hard to budge.  My only thought is the solder mask has a rougher surface than normal and the flux residue is sticking in the valleys.   I tried taking photos but it doesn't show up on camera, but the board is definitely sticky to the touch. Anybody else had a recent problem like this ?