Extremly poor customer support!
Twotrees machine quality and lack of support has been a significant reason I will never buy from them again. After receiving the TT450PRO I found several assembly workmanship errors that required correction. The machine had an intermittent issue with Z Axis probing and movement. Based on this being intermittent I passed it off to typical "Chineser Junk" (build cheap and sell crap!). The machine remained usable up until a few months after the warrenty expired. The Z Axis would not move and/or allow home to be set. Communication with customer support was HORRIBLE. They wanted videos and continued to ask irrelevant questions. Finally I isolated the problem to the Z Axis controller board. As the machine was out of warrenty I paid for the replacement part (which took a month to arrive!). After receiving the replacement board I swapped the boards and the machine worked fine. Inspection of the removed board found one of the PCB pathways had been almost entirely cut through during either fabrication or assembly. I sent a clear picture of the damage to Twotrees with a request to refund what I paid for the replacement board. They refused because the warrenty had expired.
Moral of the story: Buy a machine from someone else if customer support is important to you!