Thanks clsdclsd and davidfor!
I will try your suggestions this evening.
I tend to think that there are two kinds of mechanisms involved. 1) One (the older) part of the software presupposes that certain dictionaries are installed, or it searches in the relevant directories for them. 2) The other part of the software relies on database information about what dictionaries have been downloaded to the device. Point 2) would make sense for all devices that start out with 2.1.14, since they do not have any dictionaries installed from the outset. Since older devices inherit the dictionaries from previous firmware versions, and therefore, there is no need for downloading them, those dictionaries are unknown to the database.