At this stage I think understanding the inconsistencies on the ticket is very important. If the OP can show that the ticket contains anomalies indicating errors in the railway's ticket issuing and printing systems (and these categories of errors are not unknown), this can only strengthen the OP's case. Such anomalies may have led to suspicion of wrong-doing falling unfairly on the OP, when in truth the fault lay elsewhere. Pointing out the railway's mistakes may go some way towards reinforcing the accuracy of the OP's account.
Did you actually pay £2.90 or £4.60 for the ticket (or something else)? Please check your records. The printed ticket is not supposed to exist. It is a hybrid of two tickets.
Please confirm where it was purchased from: which website or agency?
Did you make that purchase transaction on the day of travel or on a previous day? What day and time did you buy it?
How exactly did you pay for it? (e.g. Google or Apple Pay, Mastercard Credit, Visa Debit, PayPal - which card issuer? etc.)
Also pull together whatever evidence you can that supports the fact you were in or near Mountfichet all day.