I have been playing since the Beta 2.4 release on Steam, - soon after, I switched to Frontier.com (why go thru a 3rd party?), - I lost many, many ships during the "old days" type of training when they dumped you into Open in an unaltered Sidewinder without a docking computer and chased by everybody's uncle - I learned quickly how to avoid interdictions during SuperCruise or if caught, using maneuvering skills I didn't know I had. I lost at least 1 ship-per-day during that time, barely getting a rebuy while retaining a small number of credits.
Stacking Missions was the most likely cause since I was in a hurry to gain a more useful ship, higher rankings, or the better missions I saw in the "requirements not met" section - This game is for the LONG HAUL type of play, take your time, don't get greedy, you can always go back for that next tasty mission you saw at the last location. Short term gratification is not a good play style in this game or in RL.