Can no longer select most objects with mouse pointer

How do I regain the mouse pointer select if it gets lost?

After inserting some text into a LibreCAD 2.1.2 drawing using Ubuntu 18.04, most objects could no longer be selected with the mouse pointer. They could be selected with a window. A few objects could still be selected with the pointer (a few hatch patterns, and two of a myriad of lines).

BACKGROUND
Issue started yesterday after working several hours with a drawing that is part of a garage and workshop architectural design. The set of drawings have been worked on for several years without this problem and through various versions of LibreCAD and Ubuntu.
The problem is with only one of the drawings.

It makes no difference where I pick on or near the object or text. It cannot be selected, except with a window.
Exceptions are for one line out of hundreds, where I could pick the line using a certain part of the line and not any other part of the line.

No matter where I pick with the cursor in the drawing, a single angle measure in a triangle gets selected (roof slope angle).
That angle measure will get selected even if I use a window to select a different object far away.

The drawing could be recreated without the selection glitch by importing it as a block into a new drawing and exploding it.
It would be good to know how to fix the issue without using the block insert method, because importing a block and exploding it changes the order of hatches.

Only being able to select with a window also happens when you have an image in the background. You then always select the image, even if it's layer is locked. You can only prevent this by making the layer invisible.
I would try to find out which layer is the troublemaker.

Checked the layers.
It is the layer with the dimensions.
If it is invisible then objects and text on other layers can be selected with the mouse.

What could I have done to the layer with the dimensions?

Is there an image in the background? Make all other layers invisible. Pick somewhere in the screen and do "delete".
Or delete that dimension that's always being selected. Maybe something is wrong with it. Redo it.
Just try several things to find the reason.

The layer does not have an image.

All layers made invisible except the dimensions layer.
Saw two items that were on the layer by mistake (two words and 3 lines from the notes layer, and which were coloured differently than the dimensions)
Deleted those items (rather than assigning them different layer attributes).

After deleting those items, the issue remained.

Then I deleted the angle measure that always gets picked and the problem disappeared.

Tried to add the angle dimension again and it would not set. The two lines could be chosen and the angle and arc would appear and expect me to pick the arc location and after doing that the angle dimension would disappear.
Closed and reopened program, tried again and no luck.

Okay that was dumb of me.
I had an invisible layer marked so the angle dimension went on the invisible layer.
Fixed that, so the angle dimension appeared on the dimension layer.

That created the same corrupt behaviour as before. The angle dimension would be the only item that can be picked. It is as if it creates a drawing image instead of vector entities.

Thank you.

Hi Lambertus.

I have (I think) the exact same problem. The selection issue appeared while I was editing, just when I defined a new layer (could be coincidence); I was using a background image. But now, I've removed the background image and still can't select. Closing LibreCAD and restarting doesn't solve the problem either.

Window selecting _does_ work, but, most annoyingly (as selection issues can be solved by window selecting), I can't click on a spline to change its attributes.

One extra piece of data: There are several 2-point lines at the left of my drawing. The vertical line can be selected normally (at any point), but two horizontal lines (at the top & bottom of the vertical line) can only be selected on the first few millimeters. The rest is insensitive.

Looks like there's an (invisible) image blocking the view.

Any solution found?

With View - Draft on any image should be shown as a frame or outline with a continuous line.
An invisible image could be a uniform area the colour of your screen background or transparent. Still, if you click on it, it should be selected and the frame be shown as a dotted line. Or do a Select All.
Also try to find out on which layer the culprit is by switching them on and off and trying to select some lines.  

Could someone please test this behaviour on LibreCAD 2.2_rc2? If the behaviour is still there then please file a bug.