Experiencing Http timeouts when Http calls are made from two .Net frameworks together (.Net Framework 4.8 and .Net Standerd 2.0)

I have an ASP.Net Web API built on .Net Framework 4.8 and we are using a self created nuget library which is built on .Net Standerd 2.0.

this nuget library makes Http calls to 3rd party service.

To make Http calls we are using single HttpClient object for all the calls happening to this 3rd party service.

On a certain load we are seeing Http calls are timing out.

Here We make Http calls from ASP.Net Web API (.Net Framework 4.8) also so there is mix of Http calls going from HttpClient from .Net Framework 4.8 and .Net Standerd 2.0.

With mix of HttpClient We see around 10% of Http calls are timing out.

NOTE 1: I also tried creating this nuget library on .Net 4.8 and with same HttpClient pattern and same load it works well i.e. No Http timeouts when .Net platforms are same.

NOTE 2: When I make calls only to third party service then also it works when. i.e. only http calls made from .Net Standerd 2.0.

NOTE 3: I have timeout problem only when Http calls are made from both .Net platforms (.Net Framework 4.8 and .Net Standerd 2.0. )