Hi FourKneez, i think I found the root cause. In the meantime a workaround is as follows:
Settings → Search → Autocomplete → turn off Top Hits.
However, that may be a bit annoying if yuo rely on Top Hits often, another solution is:
Give the problematic bookmark a keyword. Open it in Bookmarks → Edit → Keyword → type anything → Save.
Thank you for your help in making Orion a better browser!