Tuning shift: could it be my truss rod?

Tuning shift over night

I recently finished a new tele build and it sounds great. I really love the guitar and there is nothing I want to change with it. The only weird thing is that the tuning tends to shift when the guitar is left for a period of time (like over night). It can go flat or sharp depending if it’s gotten colder or hotter.

Now I know it’s not that unusual, but I am talking pretty small changes in temperature (from one evening playing and left out till the morning). It’s spring in California, not that much temp swing… It’s not really a concern either but I find it curious as my other guitars don’t seem to be as susceptible to it.

I started thinking if it could be that my truss rod is not tight, letting the wood move more than if it were snug. I tried to adjust it last time I changed strings and it was very loose. I turned it a half turn to just begin to feel some resistance. It’s an Allparts TMO-FAT neck.

Any ideas?