Never heard of it. Not in this country. Not to say it doesn’t happen and we don’t have incompetents too (because we do) but in a country with north of 350 million privately owned firearms, it is a matter of personal survival for police.
It obviously happens, I’ve been there.
3 separate searches miss gun in NM man’s waistband It wasn’t until he was placed through a body scanner that the firearm was noticed
https://www.corrections1.com/weapons/articles/3-separate-searches-miss-gun-in-nm-mans-waistband-Ei4NZcIjIAWTqe4X/
Video: Suspect sneaks gun into cruiser, shoots officers
https://www.police1.com/patrol-video/articles/video-suspect-sneaks-gun-into-cruiser-shoots-officers-lkDhnbFheMHLKyp9/
Video shows cop searching turnstile jumper — but missing gun tucked in waistband
https://nypost.com/2019/09/20/video-shows-cop-search-turnstile-jumper-but-miss-gun-tucked-in-waistband/
How did an inmate get a loaded gun into Cook County Jail?
A crime suspect managed to smuggle a loaded handgun into Cook County Jail after Chicago police officers and then jail officers missed the weapon in at least two separate searches
https://www.chicagotribune.com/news/ct-cook-county-jail-gun-investigation-chicago-20190710-7gpdmna52fan5dhfgguvpir5ia-story.html