Thanks for your words. I also got some flicker here and there on my mini. They don't happen on a real Amiga (check video).
I got more serious issues on other games such as Risky Woods (flicker and also stutter), I think that I reported it to the related people on Discord. The upcoming THEA1200 full size next year likely won't have these issues if it uses FPGA instead of Raspberry Pi or a stronger Raspberry Pi that enables it to handle games that make heavy use of the Amiga's Copper coprocessor.