Second Timothy 2:17-18 has always confused me. Were two guys really leading some early believers astray by claiming that the resurrection has already happened? That seems like a lot of gullibility!
But today I noticed that Paul appears to only use the Greek word anástasis (and the related words anístēmi and exanástasis) to literally to mean "stand up" when quoting from the Tenach (as in Romans 15:2 and First Corinthians 10:7).
Normally in Paul's letters those words refer not to literal rising but metaphorically to the power and purity of the now available "resurrection life".
This is most clear in Philippians 3:9-14, where Paul says he wants to know the power of Yeshua's anástasis to increasingly attain his own exanástasis.
So the heresy in Second Timothy 2:17-18 is probably the claim that complete access to "resurrection life" is available now. Paul knows better. Through faith and participation in Yeshua's sufferings we can gain more and more "resurrection life", but having it fully remains a distant goal until we reach the World to Come.