There seems to be some inaccuracies with selecting entities at coordinates at the center of blocks due to some issue with positioning.

Test:

0. Teleport to a coordinate with no decimals at the center of a block such as by /tp 0 0 0 or /tp 18 32 12.

1. /summon Pig ~ ~ ~

2. /tp ~1 ~ ~

3. /summon ArmorStand

4. /say @e[type=!Player,c=1]

5. Notice the result is the pig, rather than the armor stand which is clearly closer and you are standing inside it directly at its location.

6. /say @e[type=!Player,r=5]

7. Notice that the first result is the pig rather than the armor stand which if it was selecting correctly, should be displaying the armor stand first in the list of results due to it being closer. see MC-97316

8. Repeat test with various entities to see the same results.