The chair mat probably needs longer spikes because my carpet is not flat pile. I’ll continue to use it for a few more days but if it continues to shift I may need to return it for another one.
Prior floor matt lasted about 4 years and then just stared falling apart. That one was a replacement per a Lifetime Guarantee. But thought it a bit much to do that again and the new one is a few inches larger in both directions and reasonably priced.