I am trying to plot the EEG data using the SPM MEEGtools' Fieldtrip interactive plotting tool. The tool correctly plots the waveforms, however, when I select a single (or more) electrode(s), it shows the waveform in a another window but gives this error and the error keeps recurring as long as the electrode window is up on the screen:

I'd really appreciate if someone can explain the reason for this error or a fix to this issue.

Thanks