Hi Jarkko,
ASN is exactly the same unfortunately and i am having the same issues as your are. Its quite frustrating one aspect of VOX that I really don't like which is a shame because the program as a whole is superb.
I have emailed the creator Tegwyn and he says there is no workaround or fix for this as present but I have read that restarting VOX just prior to TOD might fix the issue for now. Not had a chance to try out the theory myself yet though. As to whether he will eventually add the function to read the weather file I'm not sure, but it would be marvellous if he did.