I have moved into this house 21 days back. The bathroom has Delta 1500 series. Since few days I was facing the issue of temperature knob getting loosen up almost everyday. Due to this I am not able to set the temperature of water correctly. I used to tighten it up with screw driver & it used to work. But from yesterday the knob is not tightening at all. It is almost free. I know that there is no issue with the cartridges. If I am able to tighten the knob properly then most probably it will work. The shower handle also works fine. I called the delta customer care and they told me to change get a 1700 series conversion kit & replace it with current one. I checked online & the cost is around 270 CAD. Please let me know if this is the only solution left? I can see that that every thing else related to the shower looks absolutely fine. It is the temperature knob that is having the issue. I am attaching photographs for easy reference. Any quick suggestions will be highly appreciated.