net_processing.cpp:
if (pindex->nHeight <= nHighestFastAnnounce) {to:
// pindex->nHeight == nHighestFastAnnounce is expected when a more
// honest-looking block replaces a selfishly-mined block.
if (pindex->nHeight < nHighestFastAnnounce) {Write a test for this as well.
See https://reviews.bitcoinabc.org/D1442 for details.