I have had T's molt on their way over, I have opened a box and put the T in its new tank and right away all it did was lay a molt mat then molt. I have had them get stuck in molts in transit. It does happen. But if you buy from someone that can see the signs of heavy premolt this can be avoided. If I ever am selling something and I think a molt is near I always wait to ship.
I have had a couple of slings molt in transit and in one case was freaked when I found what appeared to be a leg broken off when I opened the vial. It turned out just to be a broken off piece of the exuvium however. As well as one case of a T molting within 24 hours of arriving.
i have had a decent number of spiderlings molt on their way to me... a couple few larger spiders, also. so far all the spiders made it... but i had a P. imperator that molted midshipment. it didn't go so well... i had to cut the old exuvium off of the tail, which was almost tied into a simple knot. the next molt the tail straightened considerably and the scorp required no help.
I've had this happen on multiple occasions with smaller individuals. I recently had an adult female H. lividum molt in transit and luckily it turned out ok. As talkenlate04 mentioned, if there are telltale signs that a molt is coming up then it's best to wait and ship after the molt if possible!
On a similar note, i've had a couple of large, expensive things molt on the way to large animal expos and lets just say, I was swerving to miss EVERY pothole on the way
i had received a t that was sent in premolt and was in the process of molting when it was shipped.. needless to say, it arrived in bad shape and didnt make it through the night.....what was weird is that the seller knew and wondered if he should of done this:? apparently he shouldn't of..
i think if its questionable then it should wait..i understand that in alot of cases it canted be helped..but for the ones that clearly are going to molt, i think id raise red flags if the seller knowing knew this and sent it anyways....
i had a female gold earthtiger molt on her way down to me,the seller had no idea,when i got her i opened the box and looked in the container she was almost out of the molt! it was amazing,i just left her in there for a couple of days to harden up and all,she was fine! still have her,and she's a biggie also,you never know,when i told the seller he could'nt believe it,she was burrowed most of the time so he didn't know when he dug her up to ship her to me.