I've put in lots of Thermomax and Viessmann (which is the same tube) and never had this issue with them. Thermomax is defunct now so you must have got them from a reseller. No moisture on them will cause this especially just around freezing but what will is having the lower clamp too tight so the glass can't expand and contract. I can't see another reason for it breaking unless there is no vacuum in there at all and at that time you will see that there is no "getter" ring at the bottom anymore, indicating a vacuum breech.
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