Dektol can be put in stoppered bottles and will look good after after 24 hours, but the prints will be almost imperceptibally bad, something you can`t put your finger on, just not right. I was doing some tests with very careful printing and could not match previous prints. Freshly diluted Dektol solved the problem. It looked all right, just did not work right. If I recall, the highlights would look dull and if I printed longer, the blacks would go. No amount of manipulation would fix it.
I had the same thing happen to me. I hauled an enlarger to college, had all the trays set up, took the head off to see if the light would work. Bulb blew. Tried both spares. Both went. You can not buy enlarger bulbs in Lafayette, Indiana on a Sunday night in 1965 either. I since leared they bulbs are supposed to burn in a certain position. I changed the position by pulling the head up and looking inside so I caused my own problem. Was an Omega B3 machine.