Major - P3 Multiple threads can attempt page splits concurrently on the same page. Create an automated test to stress the page splits to verify that the concurrent splits do not interfere with each other.
An example wtperf configuration file that generates a lot of page splits is:
conn_config="cache_size=100MB,log=(enabled=false),statistics=[fast],statistics_log=(wait=5,json=false)" table_config="leaf_page_max=8k,internal_page_max=8k,leaf_item_max=1433,internal_item_max=3100,type=file,memory_page_max=1MB,split_deepen_min_child=100" table_count=3 icount=50000 populate_threads=1 random_range=100000000 checkpoint_threads=0 report_interval=5 run_time=10 threads=((count=20,inserts=1)) value_sz=200 key_sz=64 reopen_connection=false
Which was used to reproduce a failure in WT-3710. Ideally we'd implement this using the newer workgen rather than wtperf.