The zero date for the ObjectScript built-in $HOROLOG variable (aka $H) is 12/31/1840 so the date, 01/06,1841, you are seeing is date number 0 plus 7 days. Now the $H day number in your Error Details, 67407, is 07/21/2025 (i.e., today) and the $H time number (67118 seconds) is 06:38:38PM local time.
It looks like <INTERRUPT> was signaled while %ETN was generating the error log. The <INTERRUPT> signal usually means someone typed control-C on the terminal. The control-C may have interrupted %ETN before it had dumped all the date/time information of the original error. The $H string in your Error Details, "67407,67118" is probably the date/time when the control-C was typed.
Your error message says the %DynamicArray class does not have a %GetAt method. It has never had such a method although back in Caché 2016.1 there was an experimental array class that had a $getAt method.
You might try replacing all your .%GetAt(0) method calls with .%Get(0) method calls.
If an <INTERRUPT> occurs outside of the ^%ETN routine then ^%ETN ignores the interrupt and THROWs it back to the application code.
In this case the <INTERRUPT> occurs inside the ^%ETN routine while it is processing an earlier error signal. At the line in question, ErrST+6, the ^%ETN is executing the
Merge ^ERRORS(date,errnum)=^mtemp(State)
command which is merging the error state (in ^mtemp(State)) into the ^ERRORS(date,errnum) log variable. That could mean that ^ERRORS(date,errnum) is only partially created so it would contain corrupted information about the error trap sent to ^%ETN.
It looks like that Merge got held up for some reason allowing the user time to signal <INTERRUPT> with a ctrl-C, or some other <INTERRUPT> signal. That would cause ^%ETN to KILL ^mtemp(state) and then ^%ETN executes the following local routine which generates a minimum entry in the ^ERROR log global entry describing the error that aborted ^%ETN.
ETNMINIM
N h,d,i
S h=$H,d=$E(h,"^",1),i=$I(^ERRORS(d))
S ^ERRORS(d,i,"*COM")=h_","_$ZE_"; log entry lost."
S ^ERRORS(d,i,"*STACK",0,"V","$H")=h,^("$I")=$I,^("$J")=$J
Q
This mimimum ^ERRORS(date,count) entry describing the signal that interrupted ^%ETN should just follow the ^ERROR(date,count-1) entry that was only partially generated.