Azure APIM Calls are failing while connecting to load balancer

Question

We have hosted all our APIs in APIM and we have around 150 services hosted on to this APIM. All of sudden, from past few days we are seeing a lot of failures with a glitch of 2 minutes across with various API calls with error "A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10...*.443 {This is a load balancer IP} *Masked the ip for security purpose.

So our architecture is something like this. Customers=>AFD=>APIM=>Express route==>Load Balancer=>Backend systems.

We checked all possible logs but not able to find the RCA for this. Can you please suggest the RCA