Appeals Council and Res Judicata

Imagine this scenario: After attending two ALJ hearings, my claim is remanded for the second time from the Appeals Council. Between the two ALJ hearings, the ALJ makes certain claims that benefit my claim for disability (i.e. he determines I am disabled, but by a date after my alleged onset date). Because the claim is remanded twice, a new ALJ is assigned. Can the new ALJ re-litigate any issues that the previous ALJ decided in my favor? Based upon what I understand about Res Judicata, this would mean once the first ALJ makes decision in my favor, the subsequent ALJ cannot reverse said decisions. If so, this could open the doors to a never-ending merry-go-round type of litigation in which a claimant could literally never gain benefits if one ALJ is simply able to retry the matters that were previously to the claimant's advantage. Am I correct? If you think otherwise, please point me to precedence or documented law so I can better differentiate.