Problem with Series 500, spiral springs and 17-007 brackets

A quick learner from Woodbridge, CT says:
Recently, I purchased six Series 500, 5/8 inch diameter spiral springs and the necessary 17-007 brackets. I installed pairs of springs in three windows to replace the sixty year old original springs. After installation, each of the three windows seemed to be working properly, e.g. the sash staying in position when raised, moving smoothly in their tracks when lowered. Unfortunately, this didn't seem to last. After the window has been raised once or twice, one or both sides of the new spiral spring lets go and 'blasts' downward completely extended down to the sill. This happens especially if the window is not gently -- VERY GENTLY -- raised which happened on all three windows when the window cleaners were here. Using the Swisco tool, I have carefully reinserted the spring tabs into the 17-007 brackets, and pushed the tabs up as far possible into the brackets' 'hooks'. The tabs appear to be firmly held by the bracket, but within one or two subsequent sash raisings the springs 'explode' (I can't think of a better word to describe the event) fully extended again. I recall that the original springs were riveted permanently to the bracket on the bottom of the sash, but this is clearly not possible with replacements. Can you offer any advice to ensure that the spring's tabs stay firmly in the bracket? Thank you for your assistance.
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Paul from SWISCO responded:
Sorry to hear about the trouble. If you remove the 17-007 bracket and squeeze the fork end that might prevent the bow tie from slipping off the bracket. Let me know how that works.
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