Wordpress permalinkslug changed page to page__trashed

A Wordpress site of mine seems to have changed some of my pages permalinks by adding __trashed after the slug. Note that not all pages are affected, neither do other post types.

Anyone might have seen the same problem & a clue what might have caused it? I can remove it manualy, but it's kind of weird and I don't want it to happen again :)

I'm using WP v 4.5.3 & the plugins are up to date.

plugins used:

  • Bulletproof security
  • comet cache (former zencache, former quick cache)
  • Yoast SEO
  • Mailpoet
  • Captcha by BestWebSoft
  • Event organiser
  • ACF