If some of your banner layers include entry/exit animations on a banner that is also set to only loop a certain number of times (rather than infinitely) in HTML exports, this can end up resulting in some of your exit animations making layers invisible after the final banner playback iteration.

To resolve this issue for this scenario, you can specify any layer in your banner's timeline to remain visible after your banner's final playback iteration.

You can optionally enable this setting by clicking any layer's Settings icon button in the main timeline to open the layer settings, and enabling the Keep layer as static end frame (remove final exit animation) toggle.