Adding visual webpart to list display form

HI Sergei Gorelik,

I think the issue that you are running into is similar to one I had a while back.

In my case a view on a list was set to the default welcome page when I exported the site and PnP PowerShell wasn't able to handle the web parts on the page as the page used isn't a web part page but a view on a list.

I wouldn't be surpised if you have the same issue as you are using Add-PnPWebPartToWebPartPage to add a web part to a page that isn't a web part page. You could probably add a new page and add a list view web part and then add your custom web parts to that page.