I think you need to go back in and do some more cleaning here. Often you need to remove the logic board fully from the system as there is a second side that could have gotten wet here. As your removing the logic board you do need to practice good ESD handling as static can damage your logic board.
While Isopropyl is a good cleaner it fails to clean sugar or neutralize the lemons acid that is still present in your system.
Making sure to disconnect the battery first, Then wipe down with damp cotton swabs (Q-Tips) the areas you remember seeing the spilled drink with distilled water (not tap water!) Distilled water has nothing in it other than H2O so it won't be damaging when it dries unlike tap water which has lots of junk in it. This will dissolve the sugars and dilute the acid down.
Then go over the areas again this time with the Isopropyl alcohol as it can also act as a dryer here with the traces of water you still have on the board. I still like letting the sun dry out the board the rest of the way.
See if that helps as I fear your logic board may have a damage component or two.