diff --git a/pkg/http/client.go b/pkg/http/client.go
index 7163349..d094f6b 100644
--- a/pkg/http/client.go
+++ b/pkg/http/client.go
@@ -11,7 +11,6 @@ import (
 	"net"
 	"net/http"
 	"net/url"
-	"strconv"
 	"strings"
 	"time"
 
@@ -168,7 +167,7 @@ func (r *HTTPClient) Do(req *http.Request) (*http.Response, error) {
 
 	attempt := 0
 	var origBody []byte
-	if req.Method == "POST" {
+	if req.Method == "POST" || req.Method == "PUT" || req.Method == "PATCH" {
 		origBody, _ = io.ReadAll(req.Body)
 	}
 
@@ -179,8 +178,12 @@ func (r *HTTPClient) Do(req *http.Request) (*http.Response, error) {
 		if resp != nil && resp.Body != nil {
 			resp.Body.Close()
 		}
-		r.replaceHostIfNeeded(req) // needed for ipv6
+
+		r.replaceWithIPv6Host(req) // needed for ipv6
+
 		resp, err = r.client.Do(req)
+
+		// http 4xx and 5xx errors
 		if resp != nil && resp.StatusCode/100 >= 4 {
 			body, _ := io.ReadAll(resp.Body)
 			if body != nil {
@@ -192,6 +195,7 @@ func (r *HTTPClient) Do(req *http.Request) (*http.Response, error) {
 				}
 			}
 		}
+
 		incr := r.shouldRetry(resp, reqHasRangeHeader, err, r.cfg.GetRateLimitSleepSecs())
 		if incr > 0 {
 			attempt += incr
@@ -213,34 +217,30 @@ func (r *HTTPClient) Do(req *http.Request) (*http.Response, error) {
 	return resp, err
 }
 
-func (r *HTTPClient) replaceHostIfNeeded(req *http.Request) {
-	if strings.HasSuffix(req.Host, "download.real-debrid.cloud") || !r.supportIPv6 || !r.cfg.ShouldForceIPv6() {
+func (r *HTTPClient) replaceWithIPv6Host(req *http.Request) {
+	// don't replace host if IPv6 is not supported or not forced
+	if !r.supportIPv6 || !r.cfg.ShouldForceIPv6() {
 		return
 	}
-	// get subdomain of req.Host
-	subdomain := strings.Split(req.Host, ".")[0]
-	// check if subdomain is numeric
-	_, err := strconv.Atoi(subdomain)
-	if err == nil {
-		// subdomain is numeric, replace it with .cloud
-		req.Host = strings.Replace(req.Host, ".com", ".cloud", 1)
-		req.URL.Host = req.Host
+	// this host should be replaced
+	if !strings.HasSuffix(req.Host, ".download.real-debrid.com") {
+		return
 	}
-	// check if host is in the list of IPv6 hosts
-	found := false
+
+	req.Host = strings.Replace(req.Host, ".com", ".cloud", 1)
+	req.URL.Host = req.Host
+	// check if this host is in the list of IPv6 hosts
 	for _, h := range r.ipv6Hosts {
 		if h == req.Host {
-			found = true
-			break
+			return
 		}
 	}
-	if !found && !r.CanFetchFirstByte(req.URL.String()) {
-		req.Host = r.ipv6Hosts[rand.Intn(len(r.ipv6Hosts))]
-		r.log.Debugf("Host %s is not a valid IPv6 host, assigning a random IPv6 host: %s", req.URL.Host, req.Host)
-		req.URL.Host = req.Host
-	} else {
-		r.ipv6Hosts = append(r.ipv6Hosts, req.Host)
-	}
+
+	// if not then just assign a random IPv6 host
+	req.Host = r.ipv6Hosts[rand.Intn(len(r.ipv6Hosts))]
+	req.URL.Host = req.Host
+	r.log.Debugf("Host %s is not a valid IPv6 host, assigning a random IPv6 host: %s", req.URL.Host, req.Host)
+	// if !found && !r.CanFetchFirstByte(req.URL.String()) {
 }
 
 func (r *HTTPClient) proxyDialer(proxyURL *url.URL) (proxy.Dialer, error) {
@@ -287,9 +287,19 @@ func (r *HTTPClient) shouldRetry(resp *http.Response, reqHasRangeHeader bool, er
 	}
 	if resp != nil {
 		if resp.StatusCode == 429 {
+			// Too many requests: retry infinitely
 			time.Sleep(time.Duration(rateLimitSleep) * time.Second)
 			return 0
 		}
+		if resp.StatusCode/100 == 4 {
+			// other client errors: retry
+			return 1
+		}
+		if resp.StatusCode/100 == 5 {
+			// server errors: don't retry
+			return -1
+		}
+		// if the request has a Range header but the server doesn't respond with a Content-Range header
 		if resp.StatusCode/100 == 2 && resp.Header.Get("Content-Range") == "" && reqHasRangeHeader {
 			time.Sleep(10 * time.Millisecond)
 			return 0