Hypotension (90/52) post covishield.

My father had taken covishield on 2nd April. BP remained normal that day. Fever started at night and he took paracetamol the following morning. The next day fever and headache continued with profuse sweating, he didn't drink much water throughout the day On 4th April in the morning he had sudden muscular back pain and became unconscious for around 30 seconds. BP was 90/52 a few minutes later We gave 6-7 glasses of ORS and salt water and finally towards end of the day BP reached back to 110/70 by night. He was very dehydrated as well and so drank lots of water I want to ask if the hypotension and unconsciousness was due to combined  fever + severe dehydration , or is it a delayed side effect of the vaccine. If so , is it safe for him to take a 2nd dose of covishield. Pls note.. he takes Ecosprin AV-75 OD and 300 mg gabapentin BD. If at all it is somehow related to aspirin being a blood thinner Thanks a lot!