From the look of it, and given that you already two different slicers, it look like this may be a hardware issue. I have had very similar error messages with my cheap Chinese printer and this is ultimately why I ended up always printing via the SD card and stop worrying.

That said, the error is about the serial connection over your USB cable. I was about to write a list of suggestions, but I found out that your manufacturer already has a troubleshooting guide for your printer here.

Adding my own suggestions to those of Printrbot, this is the final troubleshooting guide (the linked page has detailed instructions for each step but 6 and 7):

1. Cycle power


2. Update your Operating System.


3. [Windows users only] run a VCP (Virtual Com Port) driver wizard


4. Check physical connections and swap power and usb cables.


5. Use a standard 2.0 USB input rather than USB 3.0, if applicable


6. Make sure that your printer is away from any potential source of EMI (Electro-Magnetic Interference). Microwaves ovens, many types of energy-saving lamps and power bricks/adapters are known offenders.


7. If possible, reduce the serial speed of your connection (revert if this does not solve the issue, as it may effect print speed and quality).


8. Flash your Printrboard

To clarify what these tips are all about:

• Step 1 is about making sure you don't have your computer and printer in "dirty states" (as in: with their serial buffer corrupted or stuck).


• Step 2-3 are about making sure you have as many known software bugs and problems patched as you can, as well as all the latest features. This is especially important if you are asking for help, as nobody is going to downgrade their own machines just to replicate a user' unique state.


• Step 4-7 are about diminishing the possibility that the signal in your cables gets disrupted and mangled along the way between the computer and the printer.


• Step 8 is like 2-3 but for your printer firmware, rather than your computer software.