Hi @Amrita_Pal!
This is a bit of a challenging issue to troubleshoot, because the error message isn't very informative. We've had some related discussion here, but we never got to the bottom of the issue. It's hard to imagine how this replace command would exceed a system limit, but the other discussion also pointed to the issue coming from that section of the do-file.
What flavor of Stata are you using (Stata/IC, SE, or MP)?
I have access to Stata/IC, and I can take a look if you share your form along with fake, example data that reproduces the error message.
Let me know if you have thoughts about what could be triggering this error! For reference, the list of system limits is here.