Could you please add a screenshot?
For me everything looks in normal size.

@hytsch Please confirm this is still an issue as I cannot reproduce it. Thanks.

@hytsch Could you check if this is still an issue with the meanwhile latest Joomla version?

I can replicate this issue in my own component. Writing instructions on how to replicate with a core component now

Steps to replicate this

• edit the file administrator\components\com_users\forms\config_domain.xml
• • add this code to create an additional field

		<field
			name="test"
			type="list"
			label="test"
			layout="joomla.form.field.list-fancy-select"
			>
			<option value="1">test1</option>
			<option value="2">test2</option>
			<option value="3">test3</option>
			<option value="4">test4</option>
			<option value="5">test5</option>
			<option value="6">test6</option>
			<option value="7">test7</option>
			<option value="8">test8</option>
			<option value="9">test9</option>
			<option value="10">test10</option>
		</field>

• view the changes by going to the options for the users component and then the second tab called email domain options

• • click on the plus to create a new entry
• • click on the new test field dropdown and you will see the error reported

• edit the file again

• • remove the line
    layout="joomla.form.field.list-fancy-select"

• view the changes as before

• • there is no scroll issue but of course you have lost the ability to have a searchable list

Conclusion
It is possibly something to do with the list-fancy-select layout when used in a subform.
Or with the repeatable-table layout as the problem is not present with the repeatable layout