yes that will be one of the next things to look at.
In general it seems to be working well at the moment, touch wood.
Occasionally it will suddenly shift in the +X direction, usually after the hated ‘graunching’ noise. It sooms to go unstable when printing several items that involve a lot of longish fast movements.
Since yesterday afternoon it’s been printing several flat objects each about 2hrs, so it’s done about 8 or 9 hours now without issues. I discovered rafts, which has helped an awful lot - the first of these prints had to be stopped due to warping.
I am surprised how well it is working now, especially as one Y-pulley has no set screw, the other on the same belt has a stripped thread and I’m not sure how the other pulleys are. I ordered a replacement set yesterday, and I have created an stl to print my own pulleys if I get into problems again
Also I found that the bottom screw was missing from the Y-axis endcap above the X-motor - the one that’s impossible to reach without taking everything apart 
I assume that could allow some additional movement on the rod…
Next is to replace the old noisy fan at the bottom
I must admit that there is a lot of useful info on the Forum and I’m learning a lot about 3D printing, mainly that it’s not like conventional printing where you can put in the paperand it will print every time.