I've probably done it a few times without a problem including the last one.

Left DM to fly to Vietnam and I had to stand at the Imm'booth for at least 10 minutes while the IO studied it, including asking the IO sitting next to him. Eventually another IO

( senior, I reckon, ) appeared and all 3 kept looking at it and looking at me. I just smiled and eventually I was stamped out. I neglected to say thank you when I was handed back my passport.

We are travelling again soon and will use SUV also never intend setting foot in DMK again.

@tonray

You say confused. Look at it this way. They had 

1.  Never seen one before and didn't understand what it was because it's quite possible they really don't know half of what they are supposed to know.

2. They were just looking for any reason to try and illicit an angry response for some reason, study the stamp for a minute, look at me for while waiting for me to say something repeated 5 or 6 times, to give themselves a reason to make the situation go wrong.

My thoughts anyway.