Joiners mentioned by Shahab are a good idea where screw holes match up on both sides. Aka Inter Screws, though obviously they only work where there is clear space between.
Door handle screws coming loose after frequent use is a common problem, especially with hollow flush doors. looking for a simple DIY solution I went through dozens of videos and web pages, but the simplest solution I found at a hardware store was 'Joiner ' a simple cylinder which allows screws to be tied from both sides. This is mainly applicable for handle type door locks, but may be applicable to round type locks with opposing screw holes. Here is how you can fix the problem for good, If it deteriorates due to metal fatigue over time you can easily replace it. watch this. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0fXNtc-O9Dw.html
