Happy to help. One of my favorite memoirs is Red Star Under the Baltic by Viktor Korzh, a high-ranking submariner during the war. It is not an academic work, but as a memoir it provides plenty of small anecdotes that explain the situation Soviet submariners faced during the war in the Baltic.

The important thing to note is that Soviet submarines were prohibited from operating in the Baltic by submarine nets during all of 1943. Only Shchuka 303, according to Korzh, managed to escape the trap of the nets during 1943.

The problem with the nets was that they were backed up by aircraft, land-based guns, mines and ships. Mines could be avoided in most cases by diving deep, near the seafloor. This would also protect the submarine from aircraft, land-based artillery and ships. It made the submarines vulnerable to nets, and Korzh describes one patrol in autumn 1942 where his submarine was caught by a net in September. It managed to escape, but only because the disabled boat submerged into a crack in the seafloor that protected it from depth charges. When nightfall came, his submarine crew was able to free their boat and escape.

Not until 1944, with the end of Finland's war, were the submarines freed to enter the Baltic again. When they did so, they entered much more strongly, for although the Soviets had not been able to sail their submarines, they had been building more in Leningrad and Kronstadt.