The issue has finally been fixed to Rebelle 7.1.3 version after struggling with the reproduction of this bug for years:
Modifying a layer (e.g. painting a short stroke or clear/cut layer) quickly after Undo / Redo and then invoking another Undo / Redo caused an unrecoverable data loss in the current layer (the bug caused loss of an entire layer, undoing caused the parts of the artwork to reappear in squares)
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