I now buy all my RHPs from Pro-Products (https://pro-products.com/). A lot of forum members here use them to. You need to call and order, which is a pain, but what can you do....
I bought one RHP from Reptile Basics, just to try, and it warped after a couple of days. Before you ask, yes it is, and was, regulated with a thermostat. Subsequent internet research indicates that this wasn't the first Reptile Basics RHP to have warped. I'm still using it and it works fine but, not too impressed. All my other RHPs are from ProProducts. He's more expensive and, granted, a bit of a hassle to order from but the product is top quality. At least none of mine have warped.
Kind of a funny story about the RB RHP. Shortly after she arrived I went to check on my BEL, Helena, and couldn't find her in her normal hide. I tried another and another but she was nowhere to be found. Finally I took everything out from the enclosure, even the paper towel substrate (she was in quarantine at the time). No sign of a pearl white snake in the black enclosure. I freaked! I was about to start tearing up the room when I saw a white reflection in the upper right corner of the enclosure. It was then I learned that the RHP had warped just enough so that a little hatchling could crawl up onto the top of it! A quick fix and she can't get up there anymore! We called her "spider-snake" for a while after that!
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Fully agree!