A controller includes an interface and storage circuitry. The interface is configured to communicate with a memory device that includes multiple memory cells organized in memory blocks. The memory device supporting programming of the memory cells with enabled or disabled program-verification. The storage circuitry is configured to disable the program-verification, and program data to a group of the memory cells in a Single Level Cell (SLC) mode using a single programming pulse, to read the data from the group of the memory cells. In response to detecting a failure in reading the data, the storage circuitry is configured to distinguish between whether the memory cells in the group belong to a defective memory block or were under-programmed, and when identifying that the memory cells in the group were under-programmed, to perform a corrective action to prevent under-programming in subsequent program operations to the memory cells in the group.