RPC Server unavailable error in TC 8.7 while waiting for an object

Yes, the reason you said might be correct i.e., TC lost the reference of the object in application due to long delay.

We have used Do while loop to get verify the actual object displayed and each mintute TC will verify for the object and if found within max limit (30000Sec) then it will exit from loop(Exit Do) otherwise after reaching max limit it will come out from the loop and gives as failure.

Actually the same code has worked properly with 7.5 version but 8.7 has too slow in execution and it is giving such error.