Just last week the Rabbanut exposed a scandal that had been narrowly avoided when a mashgiach caught a restaurant owner in Ashqelon trying to pass off non-kosher meat as kosher. It is possible that before being caught last week he had succeeded in sneaking it past the mashgiach and served non-kosher meat to his customers.

Rav Yosef Chaim Bloi, the Chief Rabbi of Ashqelon, spoke to Arutz7 about the incident. What he said about it is very interesting. He said:

It seems the owner of the restaurant was sly and it is thanks to the mashgiach that they caught his deceit. The owner would buy kosher meat, and also non-kosher meat, would remove the stamp and bring it in in the bags from the kosher meat. That is how he tried to trick the mashgiach.
Many people who had eaten there approached me - it is clear they are considered annusim - having been forced, and it is definitely possible they had only eaten kosher meat....
[People should raise their level of awareness when eating in restaurants - ] I am a Haredi rav, and I support mehadrin kashrut, but there is also the standard kashrut which is definitely no less kosher than in any other city, if not better. I have been a rav here for 30 years, and I never saw anything like this. Mishaps have happened in the past, also in chutz la'aretz, and also with the Eida Hachareidis. What I recommend to people is to be particular about glatt meat (chalak), and to at least ensure that the boss is religious.

The Eida might not like being pointed out as having had such mishaps in the past, and they would probably deny it, at least at any level similar to this one.

I agree with Rav Bloi that people should look around and be aware of what is going on. Many such incidents are exposed simply by people paying attention and being aware, knowing what they should expect to see, sensing something is not right.