Solid in Liquid Reservoir

as the temp was raising and the reservoir got damaged the autoloader took cobalt ore and loaded for repair (this works for any damaged building). I would assume that the reservoir is made of cobalt ore. When the repair is done by a dup, it will remove the cobalt ore from the storage. Normally you do not see it on any building as it does not display an internal storage (but in any case it exists and you can see that dups first bring materials for repair and then actually do the repair). In this case the internal storage was showed up together with contained storage. So the temperature was exceeding 75C (120C is boiling for pwater) and the reservoir got damaged.

Well that's a weird visual thing. Appears to be exactly what happened, as soon as it was repaired it was removed.