Transitory methane signature
The 5 micron wavelength at which the brightness becomes prominent is the key to analyzing its origin. I suspect it is literally a semi-liquid methane cloud.
The methyl micron refraction range is between 6-8 microns. The vibrational absorption frequency of the methyl and methylene molecules would match the observation.
Titan's atmosphere doesn't preclude such unusual formations. It would seem likely that due to chemical attraction the atmosphere balls up released methane byproducts from the surface into such clouds.