You have a carriage return in there which can be seen as \r when the indicator is in \codes display. As a result, the termination character of x0A is not going to work because you aren't getting a line feed character.
In the Serial configure, change the x0A constant to x0D which is the code for a carriage return (ASCII decimal 13, hex 0D).
Beyond that, you have numerous problems with your code. I'll list them in no particular order:
1. Your event structure has a value wired to the timeout terminal, but no timeout event. Thus you have a broken run arrow.
2. You are only reading based on the "Read String" value change event. Value change events occur whenever a user writes a value to a control, or a value is sent to the Value(Signalling) property node. You don't have the latter, and you have an indicator which means the user can't interact with it to change a value. That event case makes no sense why you wrote it that way. That code should probably be in the timeout event case (which is missing) and Read String Value change event removed since it can never run.
3. If you don't read your serial port often enough, (and in your code I don't see any way for VISA read to ever run), then your buffer will overflow and you'll get the --1073807252 error.
4. You have a shift register on your error wire. Most functions will not execute at all when there is an error. When you get an error in one loop iteration and you pass it to the next without handling it or clearing it, you'll start with an error in the next iteration, and code won't run. One stray error will then cause the code to never run properly again until you stop and restart your VI. NEVER PUT SHIFT REGISTERS ON ERROR WIRES. I've seen tutorials to say to do it. I've seen tutorials to say to do it. Some people may say you should. I have yet to see any actual piece of code by those people where You can use a shift register on an error wire as long as in the next iteration you do something to handle the error and clear it. I have yet to see any actual piece of code by those people where they do that correctly. To me, it's a bad idea to tell new users to put a shift register on an error wire because I guarantee they won't implement properly.
5. Not that this event case ever runs (see #2 above) but your case structure in that is wrong. You are picking out the first character in the string and see if it is a "\r" which it will never be because a single character of any type can never match a 2 character string. That "lr" is a literal forward slash followed by "r". Perhaps you think it is the \r character (backslash, not forward slash) which shows up in \codes display. That is a symbol for the single character carriage return, which you are actually getting in your string as a termination character, not the first character in the string.
6. Bytes at Port method is the wrong way to read from a serial port (despite the fact it is prominent in NI examples) pretty much 99% of the time. Once you fix everything else including the termination character, you should wire a constant there that is equal to or larger than the longest message you expect to see. In your case, you know you are looking for 16 bytes, so wire that. You can even wire a larger number since the VISA Read will terminate automatically and return the data once it gets the termination characte of a carriage return.
7. Your VISA read should be in its own loop continually reading packets of data. Tying this to an event structure and user interation seems like a bad idea and would certainly lead to buffer overrun error if you didn't read the port frequently enough to keep up with the incoming data.
Now I wonder. Did you write this code or someone else? It visually looks pretty good. It seems to even try to follow some typical VI architectures. But beyond that, the architecture is completely distorted and basically non-functional. Why did you not post this earlier? This doesn't match the VI's you posted earlier. Your earlier code showed the x0A termination character (which I can now tell you for sure is wrong), while this code uses the x0D, which is correct. Your earlier code has no possibility that I can see of giving the buffer overflow error (even with the bad termination character). Timeout error, possibly. Overflow, no way. This code, I can see how the overflow error could occur, except for the fact I don't see how the VISA read could ever possibly execute to throw the error.
Go back to your earlier simpler code. Change the term char to x0D. Run that. If you need to add the event structure and producer/consumer loop like you did in the later code, wait until you understand how they work and how dataflow works in a VI before you start to piece that code in.
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