Hantek 6000 Linear Interpolation error (Software)

Codebest

In ver 2.1.31 and 2.1.34 choosing Acquire /  Interpolation / Linear is causing strange behavior on the 50 ns and 100 ns time-base settings.   The same issue does not occur on the step or sin(x)/x settings.
This was produced by choosing Utility /  Factory setup followed by the AUTO button on CH1.   This is a 100 Mhz sine was from an HP signal generator.   It works perfectly in step or sin(x)/x modes.   and it also works perfectly fine on any other time-base other than 50 ns and 100 ns when in linear interpolation mode.  This does not appear to be a hardware issue,  it appears to be software related.  I've not found a work around so far.
This is a pure sinewave being fed to the scope,  not a burst.  

Codebest

As another example here is the same setup as above only in dot mode with linear interpolation at 50 ns / div

Codebest

More feedback on this,  it appears to be a larger issue when using a single channel.   So perhaps sampling rate plays a part.   With two channels it happens at 200 ns/div time base.