系统：ubuntu20，版本seafile9.0.2 。故障：seafdav nginx错误502，无法访问，之前seafdav是正常的好用的，停电以后出现的故障，目前seafile网页及客户端均正常，请各位大神前来帮忙解决。
以下截取两条错误日志供分析：
seafdav.error.log
2022/03/16 06:37:51 [error] 890#890: *1 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: xx.xx.com, request: "GET /seafdav HTTP/1.1", upstream: "http://127.0.0.1:8080/seafdav", host: "xx.xx.com"
2022/03/16 06:37:53 [error] 890#890: *1 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: xx.xx.com, request: "GET /seafdav HTTP/1.1", upstream: "http://127.0.0.1:8080/seafdav", host: "xx.xx.com"
2022/03/16 06:40:03 [error] 890#890: *273 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: xx.xx.com, request: "PROPFIND /seafdav/ HTTP/1.1", upstream: "http://127.0.0.1:8080/seafdav/", host: "xx.xx.com"
2022/03/16 06:40:07 [error] 890#890: *275 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: xx.xx.com, request: "PROPFIND /seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/ HTTP/1.1", upstream: "http://127.0.0.1:8080/seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/", host: "xx.xx.com"
2022/03/16 06:40:07 [error] 890#890: *275 connect() failed (111: Connection refused) while connecting to upstream, client: xxx.xxx.xxx.xxx, server: xx.xx.com, request: "MKCOL /seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/WeiXin/ HTTP/1.1", upstream: "http://127.0.0.1:8080/seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/WeiXin/", host: "xx.xx.com"
seafdav.access.log
[16/Mar/2022:06:37:51 +0000] "GET /seafdav HTTP/1.1" 502 552 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36" 0.000
[16/Mar/2022:06:37:53 +0000] "GET /seafdav HTTP/1.1" 502 552 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36" 0.000
[16/Mar/2022:06:40:03 +0000] "PROPFIND /seafdav/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "PROPFIND /seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "MKCOL /seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/WeiXin/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "HEAD /seafdav/ES%20Auto%20backup%20from%20PACM00/Picture%20backup/ HTTP/1.1" 502 0 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "PROPFIND /seafdav/ES%20Auto%20backup%20from%20PACM00/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "HEAD /seafdav/ES%20Auto%20backup%20from%20PACM00/ HTTP/1.1" 502 0 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:07 +0000] "PROPFIND /seafdav/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.004
[16/Mar/2022:06:40:07 +0000] "HEAD /seafdav/ HTTP/1.1" 502 0 "-" "Sardine/0.0" 0.000
[16/Mar/2022:06:40:08 +0000] "MKCOL /seafdav/ HTTP/1.1" 502 150 "-" "Sardine/0.0" 0.000