We had an assertion failure:

[1557129879:92922][23859:0x7f344d8497c0], t, file:wt.wt, WT_SESSION.verify: __wt_rec_row_leaf, 873: F_ISSET(r, WT_REC_UPDATE_RESTORE)

on this run on kodkod-aws: http://build.wiredtiger.com:8080/job/wiredtiger-test-format-stress-sanitizer/24031/

There is no core file. This is not the same as WT-4759 because there are no overflow pages.