LoadChainTip requires cs_main to be locked. Under some conditions, it may call ActivateBestChain. However, ActivateBestChain requires cs_main NOT to be taken when called.
bool fHaveWitness = false;
    if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == ThresholdState::ACTIVE) {
        int commitpos = GetWitnessCommitmentIndex(block);
        if (commitpos != -1) {
            bool malleated = false;
            uint256 hashWitness = BlockWitnessMerkleRoot(block, &malleated);
            
            
            
            if (block.vtx[0]->vin[0].scriptWitness.stack.size() != 1 || block.vtx[0]->vin[0].scriptWitness.stack[0].size() != 32) {
                return state.Invalid(ValidationInvalidReason::BLOCK_MUTATED, false, REJECT_INVALID, "bad-witness-nonce-size", strprintf("%s : invalid witness reserved value size", __func__));
            }
            CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0]->vin[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
            if (memcmp(hashWitness.begin(), &block.vtx[0]->vout[commitpos].scriptPubKey[6], 32)) {
                return state.Invalid(ValidationInvalidReason::BLOCK_MUTATED, false, REJECT_INVALID, "bad-witness-merkle-match", strprintf("%s : witness merkle commitment mismatch", __func__));
            }
            fHaveWitness = true;
        }
    }
    
    if (!fHaveWitness) {
      for (const auto& tx : block.vtx) {
            if (tx->HasWitness()) {