Modbus acquisition timings
It is not very frequent but it happens.
Sometimes a pair of serial devices won't talk to each other at certain baud rates.
To understand why you need to realize that baud rates are derived from a clock by dividing by an integer value. Since each device might have a very different clock rate it might happen that the real baud rates are quite different. In general they should not vary more than 3-5% if they are to communicate with no errors.
An example: your FTD chip uses a 3 MHz clock. To derive 57600 baud it needs to divide by 3000000/57600 = 52.0833. Since that's no integer the closest it can go is 52. Reverting the calculation 3000000/52 = 57692.3
You will have to do the same calculation for the Modbus device on the other side to see if they are within 3-5% of each other. Most microcontroller and transceiver datasheets include a table with the percentage error on baud rates for you to check and choose. This is also a good reason to stick to standard values but as you probably know by now that is no silver bullet. Sooner or later you will pair devices that won't be able to sync.
Be aware that these are only theoretical values, that's probably why you have no problem with your second FTD transceiver. If you want to be sure you need to hook up a scope and measure those baud rates carefully.
The solution is quite obvious: change baud rates or use a different transceiver (or change its clock rate if you can).
You can read more details here.