I think I have the same issue in 2020.2.6 HF3 and also in HF4 that you are describing.
On failover of the APE the IP Address remains as the original Active server and polling engine shows as Down until we fail back at which point polling engine shows as Up.
Open case with Tech Support actively investigating. I would suggest if you still have this problem you raise a support case.
SolarWinds solutions are rooted in our deep connection to our user base in the THWACK© online community. More than 180,000 members are here to solve problems, share technology and best practices, and directly contribute to our product development process.