Why do my wall angles keep changing on their own?

I've built a building... and am about finished... just going around doing the fine tuning.. I keep getting lines where the walls connect... they should be at 90.00... angle..straight I reset them... take a copy.. to save it... when i returen to work on it again... the one I left on the platform and the saved one... both have a large number of the wall off again!!! they go to 89.95... or 89.90... leaving me with ugly lines... anyone know how to stop this from happening?

Thanks
Kandi

This is a long standing problem. I assume the prims are not physical.
It's been called the rotation bug and poisoned prims among other things. Could be the bounding boxes interfering with each other. Be firm and replace it, don't drag copies, although it may seem to work at the time.

Create a new prim to the side of the problem, copy all the values to the new one including texture values, except one x or y position , unlink the old prim in question, note the last position value, move out of the way, and punch-in the last position value into place so the new one ends up exactly where the old one was. Delete the old one.
With joins, try giving the joined faces added shades of grey colouring to help them blend a bit, don't use transparencies.
If both sides if the wall are very much darker or lighter than the other side, make a small texture, half white and half mid-grey, then colour/darken to suit.

Making a new one will be quicker in the long run than spending time trying to fix the impossible.
There are a million other methods in this city, this is one of them.

this is something that is very easy to do accidently, i have built for two years in SL on a daily basis and this happens from time to time, the only solution it to unlink and double check your prims realign if you have too and relink again. how it happens is that sometimes as you go to cam around the build you quickly click the wrong key while the cursor is over a prim and it moves it a minute distance, or you use the the arrows keys while a edit window is active and the prim move 1 cm or rotates 1 degree.

We posted at the same time...
Yep that can happen but it would move by that 1 degree not a tenth of a degree.
Could be that though, but I doubt it this time. I have spent (wasted) a lot of time fixing these small rotations only to return. It only happens with the same prim/s each time. replacing is the best way.

Oki... thank you so much... Im going to unlink and replace.... And see what happens... Thanks for the quick responce..

Kandi

Yes your right, but sometimes I have kept banging the keyboard wondering why isn't anything happening and by then the prims move much more, sometimes I can be slow LOL. I love the idea of it being a slightly warped prim though, like wood left out in the rain.

This is a very common problem, it's known as prim-drift. Parcels near the edge and corners of sims seem more prone to it than parcels around the center. The only way to work with it:
Take a copy of your work every time you're about to leave it for a while.