At the same time, I do not know (obviously, I am not a specialist) if it's normal to see this behavior. Maybe someone with power knowledge can say yes or no.
just telling my personal experiences.
we use -48VDC (36-72V) DC-DC converters with Mikrotik devices in telco environment. in this case, the input side is isolated, otherwise you end up seeing sparks if you try just try to use a 'basic' step-down solution. you can check it with a simple continuity-tester, most probably the ground on the DC-in jack is directly connected to the ground plane _and_ the grounding screws too.
stuff from mean well is pretty affordable and extremely reliable. our CRS/CCR series devices were converted to telecom power ~3-4 years ago, and they had 0 power issues. in your case however this would mean to install another IP67 enclosure with the DC-DC converter inside - not impossible but can be challenging.