[Closed] Query for those using frames with sliding drop outs.....creaking noises???

First ride out on my Trek District singlespeed today and there's a weird clunk come creak when pedalling - almost like spokes twanging. Does it stood on the pedals or sat down, and seems to be periodic with the crank revolutions.

Its got sliding drop outs and embedded chain tug bolts in the frame.

I'm guessing the creak could be due to the drop outs not being tight or some flex somewhere.

Which faces/threads should I grease or threadlock as a first effort to stop the creak?

Or any other ideas where this weird noise could be coming from?