Main thing to remember is that all VASIS can give erroneous indications under certain weather conditions where dew point and dry bulb are close, low lying mist or light fog just sitting over the runway and finally if there is condensation on the lamps. Under these conditions especially at night with no other visual cues, do not blindly accept what you see. Check the approach angle with ILS if available or suitably sited DME.
A fatal crash at Mount Gambier in Australia where a Kingair crashed 3 miles short and on the extended centre line during the visual segment of a black night VOR approach in misty weather, was thought to be associated with possible erroneous T-VASIS light signals. The T-VASIS at that airport had a long history of reported erroneous indications. It was the first time that the pilot who had over 13,000 hours, had landed at that particular airport at night. The moral of the story is that any VASIS should be treated with great suspicion in moisture laden conditions.