idea based on @jamchamb PR in official pm3 https://github.com/Proxmark/proxmark3/pull/584

CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to this project will be documented in this file.
 This project uses the changelog in accordance with [keepchangelog](http://keepachangelog.com/). Please use this to write notable changes, which is not the same as git commit log...
 
 ## [unreleased][unreleased]
+ - 'hf mfu dumop / read'  - now retries five times. (@jamchamb)
  - Added `hf list mf` - deciphers crypto1 stream and works with first authentication and weak nested authentications (@Merlok)
  - Adjusted `lf cmdread` to respond to client when complete and the client will then automatically call `data samples` (@marshmellow42)
  - Added a bitbang mode to `lf cmdread` if delay is 0 the cmd bits turn off and on the antenna with 0 and 1 respectively (@marshmellow42)

armsrc/mifarecmd.c

@@ -330,9 +330,9 @@ void MifareUReadCard(uint8_t arg0, uint16_t arg1, uint8_t arg2, uint8_t *datain)
 		if (len) {
 			if (MF_DBGLEVEL >= MF_DBG_ERROR) Dbprintf("Read block %d error",i);
 			// if no blocks read - error out
-			if (i==0){
+			if (i == 0) {
 				OnError(2);
-			return;
+				return;
 			} else {
 				//stop at last successful read block and return what we got
 				break;

armsrc/mifareutil.c

@@ -362,10 +362,9 @@ int mifare_ultra_readblockEx(uint8_t blockNo, uint8_t *blockData) {
 }
 int mifare_ultra_readblock(uint8_t blockNo, uint8_t *blockData) {
 	#define MFU_MAX_CRC_RETRIES 5
-	uint8_t retries = 0;
 	uint8_t res;
-	
-	for (retries = 0; retries < MFU_MAX_CRC_RETRIES; ++retries) {
+
+	for (uint8_t retries = 0; retries < MFU_MAX_CRC_RETRIES; ++retries) {
 		res = mifare_ultra_readblockEx(blockNo, blockData);
 		
 		// break if OK,  or NACK.