This is what one of the limiters looked like a few minutes into first startup of my new motor build. Switched to lockouts and have had no issues.
I've had different success with the Livernois limiters. They worked very well for me. I did a whole lot of data logging different cam positions with the Livernois and Comp limiters. Both worked but the Livernois style was quicker to react to commanded retard values.
I wonder what happened to your spring? It would appear to have a bad heat treat making it brittle or had a nick in it which caused the structural integrity to be weakened. Glad nothing catastrophic happened.
I've been thinking of just adding a spring to go between the phaser and modified lockout. I have a good selection of well made springs from my curio and relic gun collecting time.
As it stands right now I'm waiting for the sun to hit my roof long enough to warm it up. Had a sideways rainstorm a few nights ago and I need to seal some shingles down. The phaser mod is going on hold for a little while.
I did manage to take enough material off of each one to equal about 9 degrees of retard. Since I'm only looking for 5 degrees max they should fit the bill just fine. I still can't see how having the home made limiters without springs would cause any harm. There is no way they can go sideways and there are still 4 open chambers for the oil to control cam position.
I do think that a spring or pair of springs would help to keep everything square "just in case". Since I don't know what forces the limiters will be under in operation I don't know how likely it is that I'm missing something could go awry.
Edit: Not sure why I didn't think of this before. I have phasers that are used for spare parts. I can easily drill the back plates and screw the modified lockouts to them. I'll secure them with permanent Loctite. The green 6xx series that's used for retaining sleeves and bearings. In fact I'll probably make the back plate hole in a manner that will allow for peening material over the screw for extra security. I could also use two drilled head screws and safety wire for positive securing.