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This kind of flashbacks are common in post traumatic stress
disorder. In this stress-or used to very severe for sufferer. If this flashback occur only 5 year back, then no need to worry.
If problem is very severe and leading to frequent interpersonal problems, then for assessment and treatment, you can visit specialist like psychiatrist
I hope this information has been both informative and helpful for you.
Wish you Good Health.
Dr. Ashish Mittal