The CYA folks at the S&W Walther PPK/S plant in Maine, thought it was enough of an issue recall all of them going back several years. However, my FN9, which has a de-cocker, and a formerly owned S&W Model 411 in .40 NEVER had an issue.
To "de-cock" on a loaded chamber, as with lowering the hammer on a single action,... fundamental gun rules apply.
"Muzzle always pointed in a safe direction".
When one expects a bang and hears nothing but a click, that in and of itself is bad.
The same can be said the other way around.
Safety, Safety, Safety... But I have tested my de-cocker with my FN9 on a loaded chamber many times, muzzle down range, and have had NO issues.
I would expect a quality pistol like Sig to maintain that high of a standard as well.
Just my .02 cents.