The bad weather bug (seemingly only in snow/frozen conditions) negatively affects regular transport capability of land units, and even amphibious transports, at least for certain units, in an inconsistent manner.
After some additional play-testing with WaW 1.18.00 (I suppose it’s the same for WiE 1.28.00), the weather transport bug does seem to be applicable universally, though like I said, inconsistently.
In a Major nation’s homeland, however, it’s particularly inconsistent in that with identical snow/frozen weather conditions, a Special
Forces unit, for example, cannot transport but can amphibious transport, whereas a Corps cannot do either.
Confirmed furthermore that this weather transport bug did not exist in the previous 1.17.00 and 1.27.00 patches, respectively: it is introduced with the latest 1.18.00 and 1.28.00 patches.