.htaccess keeps getting erased ?

Hi,
about 2 years ago or so i started a small website project using wordpress as cms, it required a lot of wordpress customization ( custom theme ) etc… once finished the site stayed the same, i didnt do any update to the content at all, it ran perfectly fine until the last 3 months or so…

I noticed that traffic went from 200-300 visits per day, to 0 visits per day, very suddently… i looked at the website and saw that the homepage loaded fine, but any other page was giving me a “not found” error.

After contacting my host they told me that the issue was with the .htaccess, they restored an old version of it and everything worked fine again. The problem was that the .htaccess didnt have anything in it, it was empty, the rewrite rules were not there, therefore since i am using custom permalink structure all pages were not found…

So anyways the issue was fixed now, but a week later it happened again, then it got fixed again and still it happened once again not long afterwards…

I am really fed up with this, i dont know what is going on ? the site ran fine without any issue for over 1 year, and only now suddently is having issues… is this a known bug or something ?

Unfortunately i do not want to update to the latest version of wordpress, this would require too much time to figure out how to make everything compatible with the latest version… this shouldnt be necessary anyways because like i said, the site was perfectly fine before…

My hosting provider did a security audit to see if my site was being hacked somehow, and apparently they found nothing suspicious… i dont know how thorough their audit was but i dont know what to do now so i am hoping someone could help me ?

As far as i can tell my site doesnt use any cron job either, its just a regular static website that never gets updated…

thanks