Alleyways To Torah

Rav Ally -
I'm not sure I understand the question. רשב"א is simply saying that in a situation of ספק the תורה has a rule which says that one should conduct oneself לחומרא. In a case of a ספק מצוה this does not make the מצוה into a definite one, it's just saying that you must conduct yourself as if it is a fully obligatory מצוה. Therefore, this does not warrant עוסק במצוה פטור מן המצוה, unless the rule is עוסק במה שהתורה מחייב פטור מן המצוה. The תורה says I can't eat bugs, does that mean that checking for bugs which may or may not be there is subject to the rule of עוסק במצוה? While the analogy isn't exact my point is that maybe not all actions that stem from the תורה are subject to עוסק במצוה פטור מן המצוה.

Dear Rav Will
You are a genius. One of the gedole hador offered the same answer.
However it is a big chiddush to say that one is not fulfilling a vadai mitzva.
The chavos daas explains that when the torah says that one must eat matza that means that he must be sure that he ate matza. As long as he is unsure as to whether he did the MITZVA of eating matza still applies.
The Shaagas Aryeh however seems to understand as you do and misafek one still has a CHIYUV but the mitzva is still a safek mitzva.
Vyesh lphalpel harbeh.
Yashar koach