Upon selection of a sell shop and a wandering trader egg the wandering trader seem to also spawn an actual wandering trader. Thus duplicating traders essentially.

If I understand you correctly, you are using a wandering trader egg for the shop creation item?
The Shopkeepers plugin usually cancels the normal shop creation item interaction. So my current guess would be that maybe one of your other plugins is undoing this cancellation.

Please try to reproduce the issue without other plugins and then step-by-step re-add plugins to identify which other plugins is interferring.

You can also check the https://github.com/Shopkeepers/Shopkeepers-Wiki/wiki/Known-Issues wiki page if there are any plugins listed there that you are using and that might explain this issue.