Here my DSA815 repair story:
Symptoms started with "IF out of range" messages and sudden calibration which took up to hours. During calibration, the analyzer showed a weird spectrum, even without any source connected. This issue suddenly disappeared and the Analyzer worked fine for a few weeks. Then it started to reappear intermittently. It also happened during startup. The analyzer remained in "Device initializing..." for up to 3 hours. Another issue was loss of TG normalisation every now and then. Whenever I opened the analyzer and attempted to repair it, it started to work normally after digging around a while. Finally, it did not show any spectrum anymore. I first thought that I killed the front end, but when it happened, there was no signal applied which exceeded the input ratings.
Upon opening, I found a cracked (and electrically shorted) tantalum capacitor next to the 3rd IF section - 47ยต/35V. After replacing it, the analyzer worked fine again. Seems the capacitor degenerated gradually until it finally shorted out. Attached a picture of the culprit.