Astigmatism

My scope is a Truss DOB. I did not build the scope so some things about it are unknown as to parts used in construction or mirror manufacture (Diag).
I am having a problem with astigmatism. This problem varies with each night. Last night it was very apparent using a 8.8 UWA Meade EP when attempting to split a double.
When focused in and out of focus the astigmatism was constant and pretty bad.
I tried rotating the primary mirror as well as the EP and there seemed to be no effect on the angle of the spikes when moving in and out of focus. This seems to point to the secondary mirror as the cause. It seems to be worse when the scope gets fairly cold.
The secondary is attached to the holder plate with some sort of material sandwiched between the metal plate and the mirror. I am not sure what the material is or what glue was used to attach the mirror. I am considering removing the mirror from the plate and reattaching it with RTV and nylon washer spacers.
I am not sure whether there could be another cause for the astigmatism in the diag other than poor glass, improper attachment, or possibly surface error that is made worse by temperature changes (annealing?).
Some times the view is very good, especially at temperatures around 80 degrees f. Then is seems to get softer and has introduced astigmatism when the temp goes under 55-60 f.
Do you think it would be best to remove the diag mirror and try reinstalling it? Would there be any possiblity of another idea to try besides reinstallion?
I am not just wanting to tear into this without some plan.
Any help with this issue would be greatly appreciated.
Floyd

I was wondering if you have a conventional diagonal holder (that cups around the diagonal), or is your scope design just an open plate that you need to attach the diag. mirror with glue/sealant in order for it not to fall on the primary?

I think the best solution would be to get a conventional diagonal holder and let the mirror sit in there freely, with only the cotton backing gently pressing on its' back to keep it into place. To install a conventional diagonal holder, may also mean having to change your spider to a conventional type too, to accept the new diagonal holder, if your original design will not accept the new holder. If you still get bad images, then you probably need to get a better quality diagonal mirror.