Centos 7.6, DLC 2.0.4.1
1) Save labels from first frame folder
2) Select new folder with frames to label
3) The previous GUI with the labels of the last frame remains and the new GUI with the new frame to label is overlaid - see screenshot

4) Closing the GUI entirely and run deeplabcut.label_frames again refreshes the GUI
going back and forth with previous and next without closing also refreshes the GUI
Thanks for pointing it out! Will be fixed in next release; see @juplabs suggestion in the meantime :)
Fixed in DLC 2.0.5.
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going back and forth with previous and next without closing also refreshes the GUI