flashing 5" wide vertical stripe with striated horizontal B/W bands

probably not under warranty.

Something is failing either due to heat or age.

If it takes a while to start flashing it is likely due to heat which may not be an overheating issue, just a sensitive part that needs replacing.

If it starts immediately, the it may be an age issue as in bad capacitors. If you take the back off, you can often tell which ones are bad from looking at the tops to see if they are convex. They must be flat or slightly concave. They are somewhat easy to replace but may be difficult to find and exact replacement.