Hi ! So basically your father has 3 issues .
1. Tardiv dyskinesia
2. Vertigo , most likely peripheral (in simple language not of brain origin)
3. Cervical spondylosis as he is using cervical collar
It's ok to use stugeron for vertigo intermittently as it won't cause or aggravate tardiv dyskinesia.
Also I want to know has he any other comorbidities e.g.
diabetes , hypertension, dyslipidemia. Sometimes drugs can cause tardiv dyskinesia. So what other drugs he is taking now ?
Next Steps
kindly consult a Neurologist for further evaluation for vertigo and rule out any serious cause .Also find out any offending drug causing tardiv .