Courtesy follow up …after 5 weeks I’m no longer needing help. Transpired that the problem was with the SiteGround server Front End optimisation options settings. Disabling JS Minification and JS Combination avoided collisions with other functionalities of the site. Pity it wasn’t looked into and dealt with by SG before the weeks of tribulation that ensued until they looked seriously at the problem and fixed it. Can close this topic thanks.
