Visual Studio 2019 does not respond after loading a solution with version 2.7.1.18

After I updated my solution projects from custom build steps to Qt/MSBuild, Visual Studio 2019 (16.10.2) would open the solution and load it, but it would take sometimes half an hour to allow user interaction with VS. Even after it became responsive, it was taking a long time to respond. Cancelling a build in progress would take a really long time, forcing me to kill VS via task manager to quit a build. Running multiple instances of Visual Studio was impossible. After reverting back to Qt Visual Studio Tools 2.5.2.1, it became responsive again.

It is definitely better with 2.5.2.1, but it is still a hit and miss... sometimes I get solutions that open right away with acceptable gui response, and other times even with 2.5.2.1 I still get that behavior.  I didn't have these problems when my projects were based on custom build steps.

When it stops responding (now with 2.5.2.1), if I kill the VS instance via task manager and re-open the same solution, then it  loads faster the second time and allows user interaction.