Would it be possible to also run ACT on one of the original nodes as well?
There was a histogram correction in 4.4 which can make it appear that latencies are worse when in fact they are the same. Because of this correction, your timeouts are more accurate and therefore slightly more aggressive - this could be causing your extra timeouts. See Write Latency Increase After Upgrade to Aerospike 4.4 or higher for details.