The following error started appearing in RESTBase logs:
Cannot read property 'substring' of null TypeError: Cannot read property 'substring' of null at Object.extractExtBody (/srv/deployment/parsoid/deploy-cache/revs/8a2c0ce70f3b548b806556247962077b9d951791/src/lib/utils/Util.js:1277:13) at Object.Util.getArgInfo (/srv/deployment/parsoid/deploy-cache/revs/8a2c0ce70f3b548b806556247962077b9d951791/src/lib/utils/Util.js:1554:25)
Its happening on requests to transform some content. Which exact content is being transformed is unknown.