You asked (in your other thread) if switching distros might help. This is not distro specific and relates to the linuxant driver, so I would correspond with linuxant directly to see if this can be resolved
I always tell people to avoid those drivers from that particular company and just buy an external serial modem, and if you don’t have a serial port, get a USB to serial adapter.
Serial modems work much better and more reliably than using sketchy software to do the job that your hardware ought to be doing for you. And you won’t have to buy a separate “license” for each machine either.
Yes, those modems are designed to eat up your valuable CPU cycles. Effectively, they “saved” a couple of cheap electronic components at the expense of your CPU! When you buy those modems, you think that you are getting it for an “attractive” price - without knowing that it is just “half-modem” only.