A large number of police units were channelled to WIN Stadium in Wollongong yesterday evening as the problem-plagued western grandstand roof again flapped in the gusty wind, scaring nearby residents.Strong winds appeared to break apart a join between two large sheets of corrugated steel, which whipped into motion near the south-west corner.At least nine police officers blocked access to the site from all directions while an engineer was called from Sydney to assess the likelihood of the sheets - which measure 3m x 10m - coming loose.WIN Sports and Entertainment Centre director Stuart Barnes said the engineer was summoned as a "precaution"."We're looking at a few roof sheets that seem to have come dislodged," he said."They're not coming off but they are flapping a bit so we're taking a precaution, mostly to make sure nothing bad happens."If the engineer says there's no danger of them coming off, the police will lift the [road block]."Police cars were positioned about 200m away from the stadium gates on Bank, Stuart, Burelli and Harbour streets, and all cars and pedestrians approaching the stadium were turned around from 6.40pm onwards.The State Emergency Service was also called to the site by a resident in a neighbouring apartment block, but could do little to assist.The State Government announced on Monday the stadium roof would be redesigned, strengthened and in use by June 8, ending a long and expensive saga that began on September 20 when bolts of the newly constructed, 130-tonne roof snapped under 75km/h winds.Engineers, builders and crane operators worked for two weeks to prevent the roof's total collapse by welding together two support struts that had broken away from the wider truss and removing 50 per cent of the total aluminium roofing to vitally reduce its weight."Prior to the cranes leaving, that was certified by the engineer as being safe," Mr Barnes said last night.