Thought that looked familiar  

 I haven't found mine to be a problem other than I find the machining on the threads and mechanism a little sloppy. The Base itself is carrying nearly zero load and the only possible way it becomes an issue is if under a heavy engrave job it starts to get a harmonic wobble up.
Quick and dirty way to sort it out would be with a bit of 50x25 Aluminium or Steel Box laid on its side cut at an angle at each end so you can get in to screw it to the chassis. The extra width will make it much more stiffer. Do it in Aluminium for preference as the generally thicker wall should soak up any vibrations better and its easier to work.
Edit: Did a quick look at AliExpress and this Mirror 1 mount looks a lot better if you want a complete replacement (height might be an issue) or buy the Mirror 2 mount and fit it to a new platform? 
https://www.aliexpress.com/item/3284592 ... 7561%23328You do not have the required permissions to view the files attached to this post.