the rest were ok except for one that was mercury starved.it worked when warm but took a lot of thrashing on the starter to get warmed up.i junked it.
So it could be even normal wear and related gas cleanup causing the trigger voltage to rise. All glowbottle starters are rated to be replaced with the lamp. Operating old starter with new lamp and/or new starter with old lamp mean (in the average) significant shortening of the life of the newer component. You may find many pieces working well, but the failure rate become so high, it usually mock the tube quality (so even good quality tubes yield too many system early failures)