Hi! If you open Osmand's search then paste the OLC straight into the "Type to search all" box at the top, then tap the first search result (shown as latitude and longitude) then for me in the UK it works fine, avoiding the trouble you described.
This seems to work even thought the OLC from the Google maps app is the short format followed by the general area given as text - I seem to remember that when Google first started doing that instead of giving the long-format OLC, OsmAnd couldn't handle it.
If you drop a pin in Google maps, you can also copy latitude/longitude instead of OLC, and paste it into OsmAnd in the same way.
Hope that helps! I speak from experience as a user, not from any inside knowledge.