Undesired switching to construction in atributes

Could someone help explain what I must be doing wrong to have, in attributes undesired checking of the construction box . I will delete the check in the box and the infinitely long lines go back to the desired length.  I bit later I will see "it's" change back to infinite line length and will find the construction box again is checked ??  This can be maybe 15 min. into the drawing. No set timing.  I am not using layer 0.

Thanks