What's the engine configuration on the bike? If it's a boxer unusual to lose compression on both cylinders equally and either way a Hall Effect Sensor problem cannot possibly affect compression.
I am still a believer in the devil you know and happily head off to Europe on an 84 bike hitting 90k miles. Slow to change simply because you will end up with some unknowns in another bike new to you. I would always have a budget of 500 for spend on a 'new' bike no matter how good it may seem so you need to factor that in too. I have always ended up spending it, be it service, tyres, fork oil, changing out stiff cables, replacing some broken part, battery or odds and ends.
The only way I see a boxer with low compression on both cylinders is a valve timing issue and that damage is almost always top end and easy to get at. Removal of a cover somewhere may allow you to see you still have a timing chain in place...unless due to a bad tensioner it has hopped a few teeth.
On a parallel twin busted head gasket between the cylinders can also do it. The plus side of that is that doing a repair job like that can be a plus point to a buyer if you do it right and keep a record of it.
Many years back a friend always had a the idea if you got such a result to first check the measurement and the compression tester. Even more recently a fellow K owner ran a test and got some bad results. Ran it again with a mate who another tester and got results within spec.
Still think if it was mine I would fix it because its going to devalue hugely for a buyer to risk unknown damage.
Just my thought.
I was faced with a major enough job early this year on the K100RT. 78k miles at the time and I put a new clutch, rear main seal, whole back end job plus other components. Still happy with the decision to do it because all the other bits were up to date and good. As things happen another bike did come up while I was away in September and did go with it. The RT has a list of potential buyers looking for it simply because they know the usual jobs are done....but I'm not selling it.
1992 K100LT June 2010 110,000 miles
1984 K100RT July 2013 36,000 miles, 90,000
1983 K100RS Nov 2018 29,000 miles, 58,600 miles
1996 K1100LT Oct 2020 37,990 miles, 48,990 miles
1984 K100 Sprint March 2023 58,000 miles, 62,000 miles