Handshake issues with MacMini and LG 4KUHD external Monitor

I have a late 2102 Mac mini (running Catalina) connected to LG27UD88 4KUHD monitor via thunderbolt to Mini Display port cable. There are serious handshake issues on fresh boot with display not coming on or taking a long time to show up or many a times not showing up at all. The same behaviour is exhibited when the computer wakes up from sleep.

I tried the monitor with my late 2012 MacBook Pro with retina 13" running Catalina but exactly the same problem.

Please done refer me to the generic troubleshoot thread on external monitor issues as I have done that already and of no help.