In July I gave up, the issue took me many 10th of waisted hours. Removed the TRB145 units and replaced them for another brand. But I have still these units and decided to give it a new try. I have made a test with firmware TRB1450_R_00.01.06.1.bin, TRB1450_R_00.02.03.2_LEGACY.bin and TRB14X_R_00.02.04.3_WEBUI.bin and the only version with which the link work is 01.06.1 version. With the other versions the transparent RS485 link just does not work. In my opinion it is caused by the server, if I use a server on my pc every fw version works as client. When I use the 01.06.1 version there is a quirck, I have to switch off and then on again the RS485 link in the menu. Then the link will be established and is stable.
What I would ask from the guys at Teltonika to try it by themselves, with SIM cards with a public ip addres (not fixed) and the dynamic dns service from dyn.com. Or is there someone who succeeded in creating a link with the newer firmware versions?