After rebuilding the master index, an error related to the "Size" field appears in the Sitecore crawling log:
ERROR: [doc=sitecore://master/{3475b1bc-8c03-4342-8d7e-f36d98d7e931}?lang=pl-pl&ver=1&ndx=sitecore_master_index]
To resolve the issue, upgrade Sitecore XC instance to Sitecore XC 10.0.0 or later.