What can be the reason for lacquer deposit on crankpin bearings of diesel engines?

Hi Cid,

Oil degradation in this form is usually related to an over exposure to heat.
Check your oil analysis ICP results and if Si is elevated this could be why the lubricant is cracking and depositing around the engine as
this could indicate fine hard contamination accessing the induction system and cracking the lubricant as the hard particle remove metal.

there are lots of other reasons but you should pick those from the normal oil testing eg Coolant loss will cause the lubricant to break down