My old Gilbert wall clock ran for years (70+) without a hitch. After having it repaired it ran for another year, no problems. Then it started ringing the hour notes at the half-hour and the single strike half hour on the hour. I stopped the pendulum, moved the hour hand to the hour and removed the minute hand replacing it pointing to 12 and restated. It will the run correctly for days, sometimes weeks and then resort to the original problem. I have done this several times but to no avail. Maybe it needs to go back to the shop, I hope not though.
You have done the right things to correct the problems your describe. It is most likely the old boy is showing his age and needs a little help to overcome some of the wear of 70+ years of service. Get him a little fixen' and he will most likely go another 70 years.