Reminds me of a Cessna 150 some years ago which was parked in that same spot. I wiggled the rudder and heard water sloshing around. The drain hole was blocked so the rudder was almost full of water.
We had a problem with strobe packs failing in our Pipers, couldn't work out why. After a bit of investigation it was narrowed to only the IFR and NVFR certified aircraft, which were used routinely for this purpose, but it still didn't answer why. One day a pack was being intermittent so we took it in to the hangar, the engineer looked over it, inspected the power leads, which were full of water. Still we couldn't work out where the water was coming from, we sealed overlaps that could leak and there was no evidence of leaks in rain or such. The engineer had an idea so we took one of the suspect aircraft flying and through cloud, sure enough the positive pressure under the aircraft was forcing moisture from outside the aircraft up into the rear drain holes, forming a spray straight onto the strobe pack fitted in the rear fuselage. Suggested fix, seaplane grommets, basically aft facing angled tubes so the airflow could not push the air into the holes in flight, a very cheap fix for a very costly problem. Experienced engineers are worth their weight in gold, literally, like good pilots they will save you a lot of costs and are worth paying more for.
I could think of several other similar situations where an engineer or pilot has saved an operator thousands through some proactive fault finding, which can not be found in a maintenance manual or tech course.
I always enjoyed working with engineers on problems, it felt like a team effort with excellent rewards when you solved an issue, and pilots and engineers definitely come at things from different angles so it can work really well when it's an obscure problem.
I just remembered another interesting incident. A student returned from an area solo in a 152, handing me the keys and said the aircraft was "running a little rough" and "down a little bit on power", not unusual to get reports like that, could be a bit of carby ice, or maybe lead fouling. In any case the student didn't seem that phased about it. A moment later we get a phone call from a concerned PPL who flew regularly at the company, they said they had "heard XXX fly overhead and it sounded very sick". So that prompted us to get the engineers to have a look immediately. They jump in, start the engine which immediately starts clanging like there is something seriously wrong and shut it down. Straight into the hangar, after not long the verdict, a recent overhaul had fitted the wrong pushrods, too long. One cylinder the rods had completely stopped working, meaning the engine was running on 3 cylinders. When we quized the student further he stated, "yeah it was running very rough and I needed full throttle just to maintain altitude back to the field"