If printer motor skips steps it should be firmware/printer issue since firmware takes care to keep speeds/acceleration within limits.
If you mean it makes pauses between lines send it might be a communication issue and you need to enable the print log and see what is going on exactly. At first you should try activating ping pong mode to make it easier to analyse and also because some printers can not handle parallel sending well as soon as a problem happens. If it now happens in ping pong mode log is also easier to interpret and you see at the time where it starts what is going on.
You can check in parallel in console if all filters are disabled, but it is limited to last x lines so might miss the time where it starts, so better activate logging for analysis.
Printers are handled in sepatate threads so normally do not influce each other. Exception would be if the pi disables usb due to emf issues, then it will disconnect all connected to the hub that gets disabled until reconnect. But that would also be visible in log and even in console.
