In a properly working Leica, all that you should hear in the slow shutter modes is a fine whirr (like a cat purring softly 😀). If it squeaks, it probably needs some cleaning and light oiling. Such can be expected of old cameras which have not seen action in many, many years. The mechanism can get dry in time. It also becomes sluggish from non-use.
If you're proficient in making minor repairs, you could probably inject a wee bit of lighter fluid into the slow speed mechanism (its hidden inside a "gear box" found on the floor of the shutter crate, under the lower baffle). You need not remove the cover of the box, all you need is to introduce some lighter fluid in it, using a syringe. The lighter fluid could soften the old lubricant and make it flow back to where it's needed. Exercise the mechanism by firing the shutter (at slow speed settings) so that the lighter fluid can flow into its innards and rouse the works. This often works if the mechanism isn't dirty. I've resurrected many long-unused cameras this way. If the camera works then reverts back, then a good CLA is the only solution.
Or you may have squeaking mouse stuck in there 😀
Jay
