Just completed a service on my 47 Vanguard, which began loading time. Amplitude was very good but all positions timed in the negative by as much as 44 seconds. When I let the power down I could hear some noise from the mainspring as if it were slipping but then catching. After further inspection the hole on the spring that attaches to the arbor was broken on one side so I replaced it. Once back together amplitude increased by 20 degrees and beat error @ .04 in the dial up position it was gaining +9 seconds. Then after a few moments the graph started shooting up and the gain hit 220+ then 360+ and kept going until it would not register. My first thought was it’s magnetized so I ran it through the demag. & it did the same thing. I let it run to see if it would maintain the level of gain. It did not at some point it dropped back down to 8 or 9 second gain. I monitored it all day and no spikes. Next day I wound the watch and the same thing happened again.
Not sure what would cause this intermittent spike. Any ideas?

Be sure the hairspring is clean. If any oil is present, coils can stick together intermittently.

Spotless. I think the alloy mainspring I used is too strong for the movement. When fully wound is when the timing irregularities occur and as it winds down it doesn’t have these spikes. I plan on changing it out with one of lower strength. Thanks for the feedback Douglas much appreciated.