If the hydraulic compensator is OK, you are down to three things: cam lobe, rocker and shim. One or more of those could be worn out from use. I assume you checked the rocker and it was OK. Assuming the cam lobe is OK too, you are down to the shim. The manual specifies substituting with the next thicker shim (standard is 5.1 mm). In your case I would measure its thickness and add to it the number you calculated. I would buy the shim with the closest higher thickness to the value you got. The reason is that, if I understand how it works, the hydraulic element can compensate for a higher thickness, but not for a smaller one.

Jl