<p>I'm getting seemingly random lines scattered across the top surface of my prints:</p>

<p><img src="https://i.stack.imgur.com/UdXPx.jpg" alt="lines1">
<img src="https://i.stack.imgur.com/gf0OH.jpg" alt="lines2"></p>

<p>Printer: Anycubic i3 mega<br>
Slicer: Cura 3.2.1<br>
Printer chosen in Cura: Prusa i3, <em>Gcode flavor</em> changed to <em>RepRap</em><br>
Cura Profile: <em>Fine</em>, "Outer before inner walls" enabled</p>

<p>What might be the reason?</p>

Our local library has a genuine Prusa i3 Mk2.5 that recently had this problem. Because of the number of fingers engaging such a system, it was not immediately discovered that a different profile had been selected in which the Z-hop was turned off.
Z-hop is a feature in which the nozzle lifts slightly (and is height-adjustable) as it moves from one portion of the print to another.
According to my brief research, Cura supports z-hop in the settings. Either it has to be activated or perhaps slightly increased. The aforementioned Prusa works great with 0.5 mm lift.