Having just looked at the pictures of ELS level on the Cromwell Tool site, it looks as if there are two grub screws at each end of the vial. The outer one may lock the end fitting, whilst the inner one may be a clamp for the vial. Hopefully these are just nipped enough to prevent any movement. Would not overtighten any of them for fear of cracking the vial.
The large horizontal one at one end looks to act as a pivot, and the large vertical screw at the other end is the one that I would attack.
If the vial is loose, it needs to be rotated on its axis so that the bubble goes to the highest point, before nipping up the clamp screw.. The vial may either be a curved tube, or it could possibly even be straight externally but ground to a curve internally.
If the vial is loose and needs to be rotated, you may need to slacken the outer grubscrew at the end with the vertical adjuster. removing the vertical adjuster screw would probably allow the end "plug" to be unscrewed to give access to the end of the vial. Once you are happy with the vial orientation, the "plug" can be refitted, locked with the grubscrew, and the vertical adjuster refitted.
Once you are happy with that, adjusting the vertical screw should just be a matter of iteration. Hopefully it will not be so slack that it moves easily to upset things again.
Hope that this is the right way to go about things.
Howard
fat fingers and useless proof reader!
Edited By Howard Lewis on 19/02/2020 16:49:49