Probably condensation.
Cause for concern - well it suggests it does not fly enough and does not get hot enough! I've seen it in engines which sit and then get a short flight. That is enough to start to drive the moisture out but the cooler parts of the engine cause it to condense.
The real concern is that there must be a lot of dampness in the engine and with a Lycoming having the cam up above the oil, corrosion is a real concern.