It’s possible this is similar to an issue frequently seen with bright, saturated colors (usually self-luminous colored LEDs) There is a lengthy chain about this issue here: Colour artefacts or breakup using ACES, and it affects many different cameras. The reasoning is a bit too complex to go into here - but it’s a well-known issue.
As a temporary fix you could try applying the CLF>LMT Neon Suppression to the problematic clips. I don’t know if the correction matrix contained in there will work for URSA cameras, but it seems to work for many other cameras. Without having had any test frames or information about the URSA Mini 4k’s spectral sensitivities when deriving the correction, I can’t 100% confirm that the two are related or if the Neon Suppression LUT will help, but it’s a quick fix you could try and see if it helps.