2017 iMac pages crashing with 'Aw Snap...' errors 11, 5

Bought my refurb 2017 imac at Christmas and in the last month have noticed pages crashing with the Aw Snap... and getting Errors 11 and 5 mainly while using Chrome. I am running 13.7.8 (22H730) on 3.4 GHz Quad-Core Intel Core i5, Radeon Pro 570 4 GB. I have tried removing history, cookies etc and take trouble to shut down tabs as I browse.