diff --git a/backend/internal/handler/payment_webhook_handler.go b/backend/internal/handler/payment_webhook_handler.go
index 6d8540d80b..b923a2a9a2 100644
--- a/backend/internal/handler/payment_webhook_handler.go
+++ b/backend/internal/handler/payment_webhook_handler.go
@@ -95,8 +95,7 @@ func (h *PaymentWebhookHandler) handleNotify(c *gin.Context, providerKey string)
 		if len(truncatedBody) > webhookLogTruncateLen {
 			truncatedBody = truncatedBody[:webhookLogTruncateLen] + "...(truncated)"
 		}
-		slog.Error("[Payment Webhook] verify failed", "provider", providerKey, "error", err, "method", c.Request.Method, "bodyLen", len(rawBody))
-		slog.Debug("[Payment Webhook] verify failed body", "provider", providerKey, "rawBody", truncatedBody)
+		slog.Error("[Payment Webhook] verify failed", "provider", providerKey, "error", err, "method", c.Request.Method, "bodyLen", len(rawBody), "rawBody", truncatedBody)
 		c.String(http.StatusBadRequest, "verify failed")
 		return
 	}
diff --git a/backend/internal/payment/provider/easypay.go b/backend/internal/payment/provider/easypay.go
index c54aba6aa9..a203aaf615 100644
--- a/backend/internal/payment/provider/easypay.go
+++ b/backend/internal/payment/provider/easypay.go
@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
 	"net/url"
 	"sort"
@@ -186,6 +187,8 @@ func (e *EasyPay) VerifyNotification(_ context.Context, rawBody string, _ map[st
 		return nil, fmt.Errorf("missing sign")
 	}
 	if !easyPayVerifySign(params, e.config["pkey"], sign) {
+		expected := easyPaySign(params, e.config["pkey"])
+		slog.Error("[EasyPay] sign mismatch", "expected", expected, "got", sign, "pkeyLen", len(e.config["pkey"]), "instanceID", e.instanceID, "paramCount", len(params))
 		return nil, fmt.Errorf("invalid signature")
 	}
 	status := payment.ProviderStatusFailed