diff --git a/scripts/utils/tls_creds_installer.py b/scripts/utils/tls_creds_installer.py
index 245520ceac4..82788523031 100755
--- a/scripts/utils/tls_creds_installer.py
+++ b/scripts/utils/tls_creds_installer.py
@@ -65,13 +65,28 @@ class TLSCredShellInterface:
         for c in range(chunks):
             chunk = encoded[c * TLS_CRED_CHUNK_SIZE : (c + 1) * TLS_CRED_CHUNK_SIZE]
             self.write_raw(f"cred buf {chunk}")
-            self.serial_wait_for_response("Stored")
+            result, output = self.serial_wait_for_response("Stored", "RX ring buffer full")
+            if not result:
+                logging.error("Failed to store chunk in the device: unknown error")
+            if output and b"RX ring buffer full" in output:
+                logging.error(f"Failed to store chunk in the device: {output}")
+                return False
+        if not 0 <= cred_type < len(TLS_CRED_TYPES):
+            logger.error(
+                f"Invalid credential type: {cred_type}. Range [0, {len(TLS_CRED_TYPES) - 1}]."
+            )
+            return False
         self.write_raw(f"cred add {sectag} {TLS_CRED_TYPES[cred_type]} DEFAULT bint")
-        result, _ = self.serial_wait_for_response("Added TLS credential")
+        result, _ = self.serial_wait_for_response("Added TLS credential", "already exists")
         time.sleep(1)
         return result
 
     def delete_credential(self, sectag, cred_type):
+        if not 0 <= cred_type < len(TLS_CRED_TYPES):
+            logger.error(
+                f"Invalid credential type: {cred_type}. Range [0, {len(TLS_CRED_TYPES) - 1}]."
+            )
+            return False
         self.write_raw(f'cred del {sectag} {TLS_CRED_TYPES[cred_type]}')
         result, _ = self.serial_wait_for_response(
             "Deleted TLS credential", "There is no TLS credential"
@@ -94,7 +109,11 @@ class TLSCredShellInterface:
             return True, None
 
         data = output.decode().split(",")
-        hash = data[2].strip()
+        logger.debug(f"Cred list output: {data}")
+        if len(data) < 4:
+            logger.error("Invalid output format from device, skipping hash check.")
+            return False, None
+        cred_hash = data[2].strip()
         status_code = data[3].strip()
 
         if status_code != "0":
@@ -102,17 +121,23 @@ class TLSCredShellInterface:
             logger.warning("Device might not support credential digests.")
             return True, None
 
-        return True, hash
+        return True, cred_hash
 
     def calculate_expected_hash(self, cred_text):
-        hash = hashlib.sha256(cred_text.encode('utf-8') + b'\x00')
-        return base64.b64encode(hash.digest()).decode()
+        cred_hash = hashlib.sha256(cred_text.encode('utf-8') + b'\x00')
+        return base64.b64encode(cred_hash.digest()).decode()
 
     def check_cred_command(self):
         logger.info("Checking for 'cred' command existence...")
         self.serial_write_line("cred")
-        result, output = self.serial_wait_for_response(timeout=5)
-        if not result or (output and b"command not found" in output):
+        result, output = self.serial_wait_for_response(
+            "TLS Credentials Commands", "command not found", store="cred"
+        )
+        logger.debug(f"Result: {result}, Output: {output}")
+        if not result:
+            logger.error("Device did not respond to 'cred' command.")
+            return False
+        if output and b"command not found" in output:
             logger.error("Device does not support 'cred' command.")
             logger.error("Hint: Add 'CONFIG_TLS_CREDENTIALS_SHELL=y' to your prj.conf file.")
             return False
@@ -294,20 +319,25 @@ def main(in_args):
         logger.info(f'Deleting sectag {args.sectag}...')
         cred_if.delete_credential(args.sectag, args.cert_type)
 
-    cred_if.write_credential(args.sectag, args.cert_type, dev_bytes)
+    result = cred_if.write_credential(args.sectag, args.cert_type, dev_bytes)
+    if not result:
+        logger.error(f'Failed to write credential for sectag {args.sectag}, it may already exist')
+        sys.exit(5)
     logger.info(f'Writing sectag {args.sectag}...')
-    result, hash = cred_if.check_credential_exists(args.sectag, args.cert_type, args.check_hash)
+    result, cred_hash = cred_if.check_credential_exists(
+        args.sectag, args.cert_type, args.check_hash
+    )
     if args.check_hash:
         logger.debug(f'Checking hash for sectag {args.sectag}...')
     if not result:
         logger.error(f'Failed to check credential existence for sectag {args.sectag}')
         sys.exit(4)
-    if hash:
-        logger.debug(f'Credential hash: {hash}')
+    if cred_hash:
+        logger.debug(f'Credential hash: {cred_hash}')
         expected_hash = cred_if.calculate_expected_hash(dev_bytes)
-        if hash != expected_hash:
+        if cred_hash != expected_hash:
             logger.error(
-                f'Hash mismatch for sectag {args.sectag}. Expected: {expected_hash}, got: {hash}'
+                f'Hash mismatch for sectag {args.sectag}. Exp: {expected_hash}, got: {cred_hash}'
             )
             sys.exit(6)
     logger.info(f'Credential for sectag {args.sectag} written successfully')