Welcome to Contractor's World! What I call the "Just Before You Go's". Their time is precious but yours is not.
"Just before you go...fix my smoking heap of a PC by tomorrow, will you?"
"Just before you go...can you make this report print backwards...and sort it in Cyrillic order?"
"Just before you go...rewrite the whole asset register module to comply with American accounting practices. [this was an Australian subsidiary]"
"Just before you go...can you change all the RAM in this server - I think it's got memory leaks."
And so on.
The solution is to hide somewhere in the building from about 16:00 onwards. Then you can't be assailed by these passing asshats at 16:45.
The other solution I did for management I could not avoid was to tell them I would fix their problem doohickey as long as they stayed back with me to test it was working afterwards. In other words, I would leave when they did. Testing could take MANY hours, perhaps even overnight... It was that or else their problems could wait until they were back at their desk tomorrow or in a few days time or whenever. Funnily, only one ever did pick unwisely...and lived to regret it by 3am.