Quick fixes for the issues people run into most, before you assume anything is actually broken.
Ghosting or faint leftover marks on the screen
Faint outlines of previous content are normal e-ink behavior, not a fault. E-ink refreshes partially most of the time to keep page turns fast, and periodically does a full refresh that clears the ghosting. If it bothers you between pages, a manual full refresh (or simply turning a couple of pages) usually clears it.
Slow or laggy page refresh
Start with a restart - it clears most temporary slowdowns. If the lag shows up on one specific document, an oversized or bloated file is often the cause; see Getting Files onto reMarkable for how the Klass-RM Uploader's large-file optimization shrinks heavy PDFs before they sync.
Pen or writing accuracy feels off
A worn nib is the most common cause - see how often to change the nib in the FAQ. If the nib is fine, run the pen calibration in settings and make sure the screen is clean; dust or residue under the tip can throw off tracking.
Unresponsive or erratic touch
Clean the screen first - oil and dust are a common cause of missed or phantom touches. A restart resolves most of the rest. If you use a case, check that it is not pressing against the edge of the screen, which can register as unwanted touch input.
Won't turn on or charge
Give it real time on the charger - a fully drained battery can take a while before the screen responds again. If nothing happens after a proper charge, try a hard restart, and rule out the cable and power source by swapping both before assuming a hardware issue.
Sync or upload problems
Most sync failures come down to your account connection or network, not the file itself. Check that you are signed in and connected, then retry. See Getting Files onto reMarkable for the official routes and a more reliable alternative.
A restart solves more than you would expect - try it before anything else. If a problem persists after a restart and the fixes above, it is worth contacting reMarkable support directly rather than guessing further.