Simulink Serial Receive Terminator not working? (R2019b)

I'm trying to read data from an Arduino through serial. I'm sending the string "4.13,3.14\n" over and over. When I use the Sereial Receive block and specify the terminator as LF ('\n'), the block just keeps receiving data until it fully captures the expected size. That means, if I specify a size of [1 20], it captures as many characters as it needs to fill that spacem including the Terminator that I just specified.

Whenever I try to specify a header, it simply doesn't read any data.

Any ideas?

The ASCII character 10 ('\n') gets recorded, even if I specified it as terminator

The block configuration