Reproduction steps:
1) Open "Repro" project I attached below and proceed to "test" scene.
2) Go into playmode - you should see jagged shadows.
3) In the hierarchy disable "AllyCapitaMiscParts(scaled down)" - shadows should be alright.
4) Now In the hierarchy enable "AllyCapitaMiscParts" - steps on shadows will be larger this time.

Notes:
1) Rendering paths other than deferred (also legacy deferred) don't have this issue.
2) Setting both Cast shadows off and receive shadows off removes stepping also setting Cast shadows to "Shadows only" works fine.

Expected result: shadows should be smooth as ones in the first screenshot.
Actual result: jagged shadows and other types of corruption.

Reproduced with: 5.3.2p2 5.4.0b4 5.2.4f1 5.1.4f1