Solar panel with broken glass produces designated Voc but far less Isc Amperage
The panel is a series/parallel arrangement of solar cells.  The open circuit voltage is determined by the type of cell and the number of them in series, regardless of quality.  With no load, they build up tension close to their mathematical limit.  Your cracked cells are still cells in series, but their other properties(current generation/series resistance) are messed up.  There may be one or more series chains of cells within that are entirely nonfunctional.  To get full open circuit voltage, only one full series chain must survive.  Under load (short circuit) the cells are not producing their full current and likely have to work through higher resistance, with the end result being much lower output.