@Smooth1... Did you read
PURCHASE A SHIELD ?
If so, you saw that this is NOT an epidemic sized problem.
Over the last (First) 3yrs of production, a VERY small percentage of Shield owners have had this problem. I'm guessing, but since this seems to be the most active S&W forum of them, it very possible that every single one of them having an RSA issue have posted here.
So Scan/Search for 'Shield Recoil Spring' and count the members saying they've had the problem and it MAY total 15
different members (meh... MAYBE a few more).
While this IS a hot topic, it's also relatively rare (considering how many Flawless Shields are out there).
Of course... Since you ARE a Glock Fan, if you feel uncomfortable that you MIGHT have an RSA issue with your Shield, there seem to be a good number of G43 owners that will trade you (I know several).

I'm betting though, that you'll love your new Shield and won't have an RSA issue, just like most of us here.