Please resolve this with an authorized dealer...
...aside from the fact that I, like Indblr, have never heard of this occurring, we ask that repair issues (of which this may be one) be handled off-line. We can't evaluate your siutation electronically.
For example, if the strap is old, is it the first one? How old is it? Did it get wet and shrink? Was it ever taken off the watch and put back on? Did someone along the life of the watch replace the springbar, possibly with an incorrect size? Was the watch bought new from an authorized dealer, or might the seller or owner have taken it off and not seated the springbar correctly? And, also, straps don't spontaneously fall off of watches --was there some pressure exerted, intentionally or unintentionally?
Please --there's no need to answer these questions and I'm not saying there was any maltreatment by you. All I'm saying is that someone needs to examine what's occurred, physically and not electronically. Springbars have been used for decades in the Swiss watxch industry, uniformly by all companies, and with few if any problems.
Good luck --I'm sure a dealer can help if needed.
Michael