As shown in the picture, some dimension arrowheads increase in size, why dimension arrowhead increases in size after blocks being exploded and how to deal with it?

Double-click the block, and select the dimension to check the Dim style and Dim scale overall, as shown in the following picture,

Chances are that the Dim style remains the same after explosion and the Dim scale overall has changed, which has made the dimension arrowhead increases in size.

Then how to solve the problem?

Enter D, press Enter to open the “Dimension Style Manager”, click Modify, as shown in the following picture,

Then the Modify Dimension Style dialog box would pop up, as shown in the following picture,

Just use overall scale of 1, then click OK to confirm your modification.