Oddly enough we had this same problem this morning with all students year groups and reg groups suddenly appearing in brackets on the first day of the new academic year in SIMS. Not great as our MIS Manager retired yesterday! Along with the brackets we also found that the registration group in a student record was in red. If we selected the drop down we could see a list of not completely relevant groups and then couldn't return to the original - as if it didn't exist. Pastoral structure etc all looked fine though. I found this on the ESS website and it worked for us. Brackets gone and registration groups all good. Hope it helps you too
https://customer.support-ess.com/csm?sys_kb_id=ff4be7121b9a74148a0311f2b24bcbe2&id=kb_article_view&sysparm_rank=5&sysparm_tsqueryId=ef1e31411bc57950455842a7b04bcb69
