H1 transfer before I94 expiry H1 extension in progress

need your advice.
I recently got a job offer . My i94 is valid till end of december 2021. My current employer has filed extension in regular processing.
new employer is willing to file H1 transfer as I94 has not expired yet. Will 2 parallel applications (transfer with new and extension with old employer)have any issues .
please share your experiences. according to many posts this is possible . but any chances of rfe on transfer?

No issues at all.

RFE is always a chance if your application packet is missing a supporting document or if USCIS needs more information/evidences etc. However I can tell you that RFE may not be just because you have a H1B EOS & transfer applications with USCIS at the same time.