Making async calls from an iPart

We have some custom .ascx iParts four our on-prem iMIS 20.2.65.9449 version, to which we applied the Telerik security update from march 2020 (Telerik version is 2020.1.219.45).
We are now trying to update the iParts to make some post async calls to a web API for integration with other systems (we need to send some notification messages about custom data used by the iParts).
The iParts use target .NET framework 4.6.2 (as per current version of iMIS) and System.Net.http runtime 4.1.1.3.
We followed recommended practices for making the async calls.

Since we made these changes, we are experiencing frequent iMIS sign-outs following an edit made using the iParts. Somehow it is more obvious when there are calls to Asi.AppContext.CurrentIdentity.UserLoginId within the iPart, which we need because we want to record which user made a particular data change.

Has anyone else had any issues with async calls from an iPart or around the use of Asi.AppContext.CurrentIdentity.UserLoginId?